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The Long Peace, by John Lewis Gaddis

The Long Peace: Inquiries into the History of the Cold War. by John Lewis Gaddis Oxford University Press. 332 pp. $24.95.

In the spectrum of historians writing about the cold war, John Lewis Gaddis belongs in the category of post-revisionists. The revisionists, mainly in the 1960’s, challenged the widespread Western view attributing the origins and development of the cold war chiefly to the expansive actions and ambitions of the Soviet Union and the attempt of the U.S. and its allies to stop and contain that expansion. The revisionists attacked that consensus from the Left, excusing the Soviet Union’s behavior as coming from a natural and justified sense of insecurity and blaming the U.S. for misunderstanding Soviet fears, for acting not in defense of freedom but in pursuit of its own economic interests, from an inordinate and irrational fear of Communism, and, in some cases, from an aggressive imperialism of its own, inherent in capitalist societies.

Gaddis, one of the first post-revisionists, is also one of the ablest and most influential. His first book, The United States and the Origins of the Cold War (1972), was a sensible and scholarly examination of the issues raised by the revisionists which for the most part refuted and rejected their interpretations. His subsequent works have placed him near the center of a newly emerging consensus that seems to take an impartial position between the two antagonistic “superpowers,” seeking to understand the position of each and willing to criticize both. His latest book is a collection of essays, most of them occasional pieces written for conferences, that provides a good opportunity for examining the strengths and weaknesses of such an approach in the hands of one of its abler practitioners.

Gaddis is a sober and hard-working professional who has read all the scholarly literature and has worked with the primary sources. As the Western nations, especially the U.S., have made new historical evidence available, he has examined it and used the results to answer some interesting and important questions. Thus he finds unsupported by evidence the charges of the revisionists that the U.S. feigned alarm at Soviet action soon after the war as an excuse for intervention, expansion, and hegemony. In fact the threat posed by the Soviets had been seen earlier, and its dangers felt far more urgently, by the free nations of Europe. Their chief concern was to get the Americans to take the lead in stopping it. The U.S. did not press itself upon unwilling allies but was eagerly invited to extend its involvement and influences. If American actions can be called expansion, this was “expansion by invitation.” Far from seeking to establish a sphere of influence in Western Europe, as George Kennan advised it to do soon after the war, the U.S. tried hard to establish an independent set of free, European nations that could and would defend themselves and permit the Americans to reduce their involvement.

Why did the attempt fail? Gaddis’s answer is sensible and convincing:

The reason, almost certainly, is that the Europeans themselves did not want it. Confronted by what they perceived to be a malevolent challenge to the balance of power from the East, they set about inviting in a more benign form of countervailing power from the West rather than undertake the costly, protracted, and problematic process of rebuilding their own. The United States, with some reluctance, went along.

Perhaps the most interesting question illuminated by the availability of new evidence concerns the American attitude toward the Communist world. The traditional view is that American statesmen always looked on the Communist movement in the world as a unit and failed to exploit the real divisions among Communist nations in the interests of the United States. Gaddis, on the contrary, suggests that “despite what they said in public, American policy-makers at no point during the postwar era actually believed in the existence of an international Communist monolith.” He sees the Eisenhower administration as seeking to create a “wedge through pressure,” particularly between the Soviet Union and China. The hard line taken on the islands of Quemoy and Matsu, for example, was not merely a response to domestic political pressure but also was meant “to undermine the relationship between Moscow and Beijing.” Nixon’s later opening to China is seen as a continuation of the earlier policy, where “a public policy of hard-line anti-Communism created greater opportunities for exploiting differences within the Communist world than did less rigid ideological stances.”

_____________

Such interpretations are well-argued and persuasive, but too much of this sort of thing will earn a post-revisionist scholar a reputation as a cold warrior. To avoid such a stigma requires a considerable effort to look at matters from the Soviet side, and such efforts are not lacking in these essays. Even while conceding that Americans’ fear of “Soviet and/or Communist expansionism” has been genuine, Gaddis says that “Fear, after all, can be genuine without being rational. And as Sigmund Freud once pointed out, even paranoids can have real enemies.” But nothing in these essays or anywhere else shows that American fears—and those of many others—have been unfounded. With Soviet intentions unknown and unlikely ever to be documented, why should Americans be thought insane, especially since Gaddis more than once calls their reactions to the perceived danger sensible and restrained?

Much of the revisionist case for the absence of Soviet evil intentions rests on the fact that the Soviets never did invade Western Europe or other places, nor did Communist parties in the West undertake revolutions. In the same spirit, Gaddis cites with approval the view that “The security of nations now rests . . . not so much on the exertions they themselves make, but on the restraint exhibited by their adversaries.” But what has created that restraint (such as it is) is precisely exertions like the Marshall Plan, NATO, nuclear weapons, and the demonstrated capacity and will to make use of such devices. The measures taken to achieve deterrence and containment of Soviet ambition tend to be ignored in analyses like Gaddis’s and their results taken for granted.

The last essay in this collection, “The Long Peace: Elements of Stability in the Postwar International Systems,” presents Gaddis’s current understanding of developments since 1945. Here he argues, contrary to conventional thinking among theorists of international relations, that the “bipolar” system may in fact be more stable than the “multipolar” alternative, because it happens to reflect the realities of power. The distance between the two great powers, their relative lack of mutual communication and interdependence, may, paradoxically, be a force for stability. The presence of nuclear weapons has had a sobering effect on statesmen on each side. Technological innovation, by permitting mutual surveillance, has also had a stabilizing effect. Ideological hostilities have modified and yielded to the practical needs of mutual survival. Thus, the period 1945-87 might better be seen as one of “Long Peace” than of cold war.

Gaddis is attracted by ideas arising from game theory to help explain why the “Long Peace” evolved and continues and what is needed to preserve it. The problem with this approach, as with the “evenhanded” analysis of the cold war, is that it treats all players as fundamentally the same and thereby loses touch with reality. The United States and the Soviet Union not only have very different political and constitutional systems and moral attitudes; more to the point, they have had quite different goals. The Soviets have wanted to change the balance of power in the world in their favor, while the United States has tried to maintain the status quo as much as possible. To preach, therefore, as Gaddis does, that stability requires “a sense of caution, maturity, and responsibility on both sides,” is pointless if one side wants not stability but change. In those circumstances, stability must require that the nation seeking it should be strong and determined enough to deter reckless actions by the dissatisfied power. Up to now the United States has been willing to pay the price. Whether it will continue to do so will determine if the “Long Peace” will persist.

Power Brokers

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The Long Peace: Inquiries Into the History of the Cold War First Edition

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• Publication date February 2, 1989
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• Publisher ‏ : ‎ Oxford University Press; First Edition (February 2, 1989)
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• > Journals
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• > The long peace, the end of the cold war, and the failure...

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The long peace, the end of the cold war, and the failure of realism.

Published online by Cambridge University Press:  22 May 2009

Three of the more important international developments of the last half century are the “long peace” between the superpowers, the Soviet Union's renunciation of its empire and leading role as a superpower, and the post-cold war transformation of the international system. Realist theories at the international level address the first and third of these developments, and realist theories at the unit level have made an ex post facto attempt to account for the second. The conceptual and empirical weaknesses of these explanations raise serious problems for existing realist theories. Realists contend that the anarchy of the international system shapes interstate behavior. Postwar international relations indicates that international structure is not determining. Fear of anarchy and its consequences encouraged key international actors to modify their behavior with the avowed goal of changing that structure. The pluralist security community that has developed among the democratic industrial powers is in part the result of this process. This community and the end of the cold war provide evidence that states can escape from the security dilemma.

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1. See Mearsheimer , John J. , “ Back to the Future: Instability in Europe After the Cold War ,” International Security 15 ( Summer 1990 ), pp. 5 – 56 CrossRef Google Scholar ; and Waltz , Kenneth M. , “ The Emerging Structure of International Politics ,” paper presented at the annual meeting of the American Political Science Association , San Francisco , 30 August–2 09 1990 Google Scholar . For an argument that the recent changes make realism and, in particular, realist scholars more relevant to the practice of international relations, see Walt , Stephen M. , “ The Renaissance of Security Studies ,” International Studies Quarterly 35 ( 06 1991 ), pp. 211 –39 CrossRef Google Scholar . For a critique, see Kolodziej , Edward A. , “ Renaissance in Security Studies? Caveat Lector! ” International Studies Quarterly 36 ( 12 1992 ), pp. 421 –38 CrossRef Google Scholar .

2. See, for example, Deudney , Daniel and Ikenberry , G. John , “ The International Sources of Soviet Change ,” International Security 16 ( Winter 1991 – 1992 ), pp. 74 – 118 CrossRef Google Scholar ; Deudney , Daniel and Ikenberry , G. John , “ Soviet Reform and the End of the Cold War: Explaining Large-scale Historical Change ,” Review of International Studies 17 ( Summer 1991 ), pp. 225 –50 CrossRef Google Scholar ; and Kenneth A. Oye, “Explaining the End of the Cold War: Morphological and Behavioral Adaptations to the Nuclear Peace,” in Richard Ned Lebow and Thomas Risse-Kappen, eds., International Relations Theory and the End of the Cold War , forthcoming.

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5. Morgenthau , Hans J. , Politics Among Nations ( New York : Knopf , 1948 ) Google Scholar . Subsequent references to Morgenthau are from the fourth edition of this work (see below).

6. Morgenthau , , Politics Among Nations , 4th ed. ( New York : Knopf , 1966 ), especially pp. 347 –49 Google Scholar , from which the quotations are drawn.

7. Waltz , Kenneth N. , Theory of International Politics ( Reading, Mass. : Addison-Wesley , 1979 ) Google Scholar .

8. See ibid. , especially pp. 168–70, from which the quotations are drawn; and Waltz , Kenneth N. , “ The Stability of a Bipolar World ,” Daedalus 93 ( Summer 1964 ), pp. 881 – 909 Google Scholar . On the question of the relative stability of bi- and multipolarity, also see Deutsch , Karl W. and Singer , J. David , “ Multipolar Power Systems and International Stability ,” World Politics 16 ( 04 1964 ), pp. 390 – 406 CrossRef Google Scholar ; Rosecrance , Richard N. , “ Bipolarity, Multipolarity, and the Future ,” Journal of Conflict Resolution 10 ( 09 1966 ), pp. 314 –27 CrossRef Google Scholar ; and Christensen , Thomas J. and Snyder , Jack , “ Chain Gangs and Passed Bucks: Predicting Alliance Patterns in Multipolarity ,” International Organization 44 ( Spring 1990 ), pp. 137 –68 CrossRef Google Scholar .

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10. Ibid. , especially pp. 123–28.

11. Waltz , Kenneth N. , The Spread of Nuclear Weapons: More May be Better , Adelphi Paper no. 171 ( London : International Institute for Strategic Studies , 1981 ), pp. 3 – 8 Google Scholar .

12. Waltz , Kenneth N. , “Reflections on Theory of International Politics ,” in Keohane , Robert O. , ed., Neorealism and Its Critics ( New York : Columbia University Press , 1986 ), p. 327 Google Scholar .

13. Waltz , Kenneth N. (1990), “The Emerging Structure of International Politics,” manuscript pp. 1 and 13 Google Scholar .

14. Waltz , Kenneth N. , “ The Emerging Structure of International Politics ,” International Security 18 ( Fall 1993 ), pp. 44 – 79 CrossRef Google Scholar .

16. See “Statement of the Under Secretary of Defense for Research and Engineering,” in U.S. Congress , The FY 1987 Department of Defense Program for Research and Engineering , 99th Cong., 2d sess, 18 02 1986 , p. II – 11 Google Scholar ; U.S. Department of Defense , The Department of Defense Critical Technologies Plan , 15 03 1989 Google Scholar ; U.S. Congress, Office of Technology Assessment , Arming Our Allies: Cooperation and Competition in Defense Technology , OTA-ISC-449, 05 1990 Google Scholar ; and Aviation Week & Space Technology , 20 May 1991, p. 57.

17. Morgenthau , , Politics Among Nations , pp. 106 –44 Google Scholar .

18. On typical errors of evaluating power, see ibid. , pp. 149–54.

19. Ibid. , p. 114.

20. Waltz , , Theory of International Politics , pp. 131 Google Scholar and 180–81.

21. Ibid. , pp. 180–81.

22. United Nations , Statistical Yearbook 1948 ( Lake Success, N.Y. : United Nations , 1949 ), Table 1 Google Scholar .

23. Evangelista , Matthew A. , “ Stalin's Postwar Army Reappraised ,” International Security 7 ( Winter 1982 – 1983 ), pp. 110 –68 CrossRef Google Scholar .

24. Beckman , Peter R. , World Politics in the Twentieth Century ( Englewood Cliffs, N.J. : Prentice-Hall , 1984 ), pp. 207 –9, and 235–38 Google Scholar .

25. See Waltz , , “The Emerging Structure of International Politics” ( 1990 ), pp. 1 – 2 , 29 Google Scholar ; Mearsheimer, “Back to the Future”; and Christensen and Snyder, “Chain Gangs and Passed Bucks.”

26. Based on interviews with various scholars at the annual meeting of the American Political Science Association, Washington, D.C., 1–4 September 1993; and personal communication (letter) from Stephen Walt, 20 October 1993.

27. The New York Times , 30 October 1993, p. A1.

28. Waltz , , “The Emerging Structure of International Politics” ( 1993 ), p. 54 Google Scholar .

29. Morgenthau , , Politics Among Nations , p. 114 Google Scholar .

30. Waltz , , Theory of International Politics , p. 131 Google Scholar .

31. The same point is made by Wagner , R. Harrison , “ What Was Bipolarity? ” International Organization 47 ( Winter 1993 ), pp. 77 – 106 CrossRef Google Scholar .

32. The two most prominent examples can be found in Gilpin , Robert , War and Change in World Politics ( New York : Cambridge University Press , 1981 ) CrossRef Google Scholar ; and Kennedy , Paul , The Rise and Fall of the Great Powers: Economic Change and Military Conflict from 1500 to 2000 ( New York : Random House , 1987 ) Google Scholar .

33. Waltz , , “The Emerging Structure of International Politics” ( 1990 ), pp. 7 – 8 Google Scholar .

34. This literature is reviewed by Levy , Jack S. , “ Declining Power and the Preventive Motivation for War ,” World Politics 40 ( 10 1987 ), pp. 82 – 107 CrossRef Google Scholar ; and Lebow , Richard Ned , “Thucydides, Power Transition Theory, and the Causes of War,” in Lebow , Richard Ned and Strauss , Barry S. , eds., Hegemonic Rivalry: From Thucydides to the Nuclear Age ( Boulder, Colo. : Westview Press , 1991 ), pp. 125 –68 Google Scholar .

35. See Organski , A.F.K. , World Politics , 2d ed. ( New York : Knopf , 1967 ), pp. 202 –3 Google Scholar ; Organski , A.F.K. and Kugler , Jacek , The War Ledger ( Chicago : University of Chicago Press , 1980 ), chaps. 1 and 3 Google Scholar ; Modelski , George , “ The Long Cycle of Global Politics and the Nation-State ,” Comparative Studies of Society and History 20 ( 04 1978 ), pp. 214 –35 CrossRef Google Scholar ; Thompson , William R. , ed., Contending Approaches to World System Analysis ( Beverly Hills, Calif. : Sage , 1983 ) Google Scholar ; Väyrynen , Raimo , “ Economic Cycles, Power Transitions, Political Management, and Wars Between Major Powers ,” International Studies Quarterly 27 ( 12 1983 ), pp. 389 – 418 CrossRef Google Scholar ; and Gilpin, War and Change in World Politics . Doran and Parsons argue that this is only one of the situations in which hegemonic war is likely. See Doran , Charles F. and Parsons , Wes , “ War and the Cycle of Relative Power ,” American Political Science Review 74 ( 12 1960 ), pp. 947 –65 CrossRef Google Scholar .

36. Gilpin , , War and Change in World Politics , pp. 191 –92 and 197 Google Scholar .

37. Ibid. , pp. 192–97.

38. Ibid. , pp. 231–4.

39. Personal interviews with Mikhail Gorbachev, Anatoliy Dobrynin, Oleg Grinevsky, Georgyi Shakhnazarov, and Vadim Zagladin, Moscow, New York, Stockholm, Toronto, and Vienna, 1989–93. See also Herman , Robert , “Soviet New Thinking: Ideas, Interests, and the Redefinition of Security,” Ph.D. diss., Department of Government, Cornell University , in preparation Google Scholar .

41. On the analogy, see Lebow , Richard Ned , “Superpower Management of Security Alliances: The Soviet Union and the Warsaw Pact,” in Broadhurst , Arlene Idol , ed., The Future of European Alliance Systems ( Boulder, Colo. : Westview Press , 1982 ), pp. 185 – 236 Google Scholar ; and the following three chapters in Lebow and Strauss, Hegemonic Rivalry : Gilpin , Robert , “Peloponnesian War and Cold War” pp. 31 – 52 Google Scholar ; Lebow , , “Thucydides, Power Transition, and the Causes of War,” pp. 125 –68 Google Scholar ; and Evangelista , Matthew A. , “Democracies, Authoritarian States, and International Conflict,” pp. 213 –34 Google Scholar .

42. Thucydides , , The Peloponnesian War , trans. Crawley , Richard ( New York : Random House , 1982 ), p. 44 Google Scholar . Gilpin cites this paragraph in support of his own argument; see War and Change in World Politics , p. 207.

43. See Gaddis , John Lewis , “One Germany—in Both Alliances,” The New York Times , 21 03 1990 , p. A21 Google Scholar ; Walt , Stephen M. , “ The Case for Finite Containment: Analyzing U.S. Grand Strategy ,” International Security 14 ( Summer 1989 ), pp. 5 – 49 CrossRef Google Scholar ; Eagleburger , Lawrence , speech at Georgetown University, 13 September 1989, The New York Times , 16 09 1989 , p. A1 Google Scholar ; and Mearsheimer, “Back to the Future.” The latter argues that because the West wants to maintain the peace, “It therefore has an interest in maintaining the Cold War order, and hence has an interest in the continuation of the Cold War confrontation; developments that threaten to end it are dangerous” (p. 52).

44. For a description of the several post–cold war schools of foreign policy that have developed in Russia, see Arbatov , Alexei G. , “ Russia's Foreign Policy Alternatives ,” International Security 18 ( Fall 1973 ), pp. 5 – 43 CrossRef Google Scholar . For the views of critics of the Gorbachev–Yeltsin accommodation with the West, see the interviews in Remnick , David , Lenin's Tomb: The Last Days of the Soviet Empire ( New York : Random House 1993 ), passim Google Scholar .

45. See Mearsheimer , , “Back to the Future,” pp. 53 – 54 Google Scholar ; Waltz , , “The Emerging Structure of International Politics,” p. 8 Google Scholar ; Bunce , Valerie , “ Soviet Decline as a Regional Hegemon: The Gorbachev Regime and Eastern Europe ,” Eastern European Politics and Societies 3 ( Spring 1989 ), pp. 235 –67 CrossRef Google Scholar ; Bunce , Valerie , “ The Soviet Union Under Gorbachev: Ending Stalinism and Ending the Cold War ,” International Journal 46 ( Spring 1991 ), pp. 220 –41 CrossRef Google Scholar ; and Oye, “Explaining the End of the Cold War,” in Lebow and Risse-Kappen, International Relations Theory and the End of the Cold War , chap. 3.

46. On the Soviet economy and military spending in the 1970s, see U.S. Congress, House Permanent Select Committee on Intelligence , CIA Estimates of Soviet Defense Spending ( Washington, D.C. : Government Printing Office , 1980 ) Google Scholar ; and Holzman , Franklyn D. , “ Politics and Guesswork: CIA and DIA Estimates of Soviet Military Spending ,” International Security 14 ( Fall 1989 ), pp. 101 –31 CrossRef Google Scholar .

47. On Brezhnev and his response to the Soviet Union's economic problems, see Breslauer , George W. , Khrushchev and Brezhnev as Leaders: Building Authority in Soviet Politics ( London : Allen and Unwin , 1982 ), pp. 137 – 268 Google Scholar ; Gelman , Harry , The Brezhnev Politburo and the Decline of Détente ( Ithaca, N.Y. : Cornell University Press , 1984 ) Google Scholar ; and Anderson , Richard , “Competitive Politics and Soviet Foreign Policy: Authority-building and Bargaining in the Brezhnev Politburo,” Ph.D. diss., Department of Political Science, University of California at Berkeley , 1989 Google Scholar .

48. Evangelista, “Stalin's Postwar Army Reappraised.”

49. The quotation is from Waltz , , “The Emerging Structure of International Politics,” p. 8 Google Scholar .

50. See Oye, “Explaining the End of the Cold War,” for such an argument.

51. The New York Times , 28 August 1980, p. A4.

52. For attempts at such explanations, see Richard Ned Lebow, “When Do Leaders Initiate Conciliatory Policies,” in Lebow and Risse-Kappen, International Relations Theory and the End of the Cold War ; and Janice Gross Stein, “Political Learning by Doing: Gorbachev as Uncommitted Thinker and Motivated Learner,” in this issue of International Organization .

53. See, for example, Stuart , Douglas and Tow , William , The Limits of Alliance: NATO Out-of-Area Problems Since 1949 ( Baltimore, Md. : Johns Hopkins University Press , 1990 ) Google Scholar ; Risse-Kappen , Thomas , The Zero Option: INF, West Germany, and Arms Control ( Boulder, Colo. : Westview Press , 1988 ) Google Scholar ; and Eichenberg , Richard C. , “Dual Track and Double Trouble: The Two-Level Politics of INF,” in Evans , Peter B. , Jacobson , Harold K. , and Putnam , Robert D. , Double-edged Diplomacy: International Bargaining and Domestic Politics ( Berkeley : University of California Press , 1993 ), pp. 45 – 76 Google Scholar .

54. I include the following countries in this community: Iceland, Ireland, the United Kingdom, Norway, Sweden, Denmark, Finland, Portugal, Spain, France, Belgium, Luxembourg, Netherlands, Germany, Switzerland, Austria, Canada, United States, Mexico, Japan, South Korea, Philippines, Taiwan, Singapore, Australia, and New Zealand.

55. Deutsch , Karl W. et al. , Political Community and the North Atlantic Area ( Princeton, N.J. : Princeton University Press , 1957 ), pp. 5 – 6 Google Scholar .

56. Lebow , , “Ireland,” p. 264 Google Scholar .

57. The Irish Army plan called for a border incident to be staged as the pretext for invasion. A Republic ambulance, requested by a Catholic physician in Londonderry, was to be fired on while crossing the Craigavon Bridge. In response, the Sixth Brigade of the Irish Army was to secure the bridge and march into Londonderry. Meanwhile, an armored column would cross into the southeastern corner of Ulster and strike at Lurgan and Toome Bridge, cutting off Belfast from the rest of Ulster. The two forces were to link up and “liberate” Belfast. The plan assumed noninterference by the British Army. See Lebow , Richard Ned , “Ireland,” in Henderson , Gregory , Lebow , Richard Ned , and Stoessinger , John G. , eds., Divided Nations in a Divided World ( New York : David McKay , 1974 ), p. 247 Google Scholar .

58. See NATO Heads of Government, Copenhagen Declaration, 7 June 1991; “New Strategic Concept,” Communiqué of NATO Summit, Rome, 8 November 1991; Ministerial Meeting of the North Atlantic Council in Athens, Final Communiqué, 10 June 1993; and Statement Issues at the Meeting of the North Atlantic Cooperation Council in Athens, 11 June 1992. For public opinion data, see “Europabarometer 36-Herbst 1991,” Frankfurter Allgemeine Zeitung , 9 December 1991; and Asmus , Ronald D. , “ National Self-confidence and International Reticence ,” document no. N-3522-AF ( Santa Monica, Calif. : RAND Corp. , 1992 ) Google Scholar .

59. Personal interviews with various officials in Lisbon, Madrid, Paris, Brussels, the Hague, Bonn, Rome, and Copenhagen, 1991–93.

60. Personal interviews in Wellington, Canberra, and Tokyo.

61. See Palmer , Diego Ruiz , French Strategic Options in the 1990s , Adelphi Paper no. 260 ( London : International Institute for Strategic Studies , 1991 ) Google Scholar . Pond , Elizabeth , in Beyond the Wall: Germany's Road to Unification ( Washington, D.C. : Brookings Institution , 1993 ), p. 66 Google Scholar , quotes interviews with NATO officials. See also Haglund , David G. , Alliance Within the Alliance? Franco–German Military Cooperation and the European Pillar of Defense ( Boulder, Colo. : Westview Press , 1991 ) Google Scholar .

62. Deutsch , et al. , Political Community in the North Atlantic Area , pp. 28 and 68 Google Scholar .

63. Ibid. , pp. 66–67.

64. Havel , Václav , “How Europe Could Fail,” New York Review of Books , 18 11 1993 , p. 3 Google Scholar .

65. There is considerable research that argues that democratic governments do not fight other democratic governments. See, for example, Chan , Steve , “ Mirror, Mirror on the Wall … Are Freer Countries More Pacific? ” Journal of Conflict Resolution 20 ( 12 1984 ), pp. 617 –40 CrossRef Google Scholar ; Maoz , Zeev and Abdolai , Nasrin , “ Regime Types and International Conflicts, 1816–1976 ,” Journal of Conflict Resolution 33 ( 03 1989 ), pp. 3 – 36 CrossRef Google Scholar ; and Schweller , Randall L. , “ Domestic Structures and Preventive War: Are Democracies More Pacific? ” World Politics 44 ( 01 1992 ), pp. 235 –69 CrossRef Google Scholar .

66. Deutsch , et al. , Political Community in the North Atlantic Area , pp. 117 –61 Google Scholar .

67. A similar argument has been made by Goldgeier , James M. and McFaul , Michael , “ A Tale of Two Worlds: Core and Periphery in the Post–cold War Era ,” International Organization 46 ( Spring 1992 ), pp. 467 –91 CrossRef Google Scholar .

68. For an elaboration, see Ashley , Richard , “ The Poverty of Neorealism ,” International Organization 38 ( Spring 1984 ), pp. 225 –86 CrossRef Google Scholar ; Wendt , Alexander , “ The Agent–Structure Problem in International Relations Theory ,” International Organization 41 ( Summer 1987 ), pp. 335 –70 CrossRef Google Scholar ; and Dessler , David , “ What's at Stake in the Agent–structure Debate ,” International Organization 43 ( Summer 1989 ), pp. 441 –73 CrossRef Google Scholar .

69. Waltz , , Theory of International Politics , p. 90 Google Scholar .

70. Waltz , , “Reflections on Theory of International Politics ,” p. 329 Google Scholar .

71. See Waltz , , Theory of International Politics , p. 118 Google Scholar ; and Waltz , , “Reflections on Theory of International Politics ,” pp. 330 –31 Google Scholar .

72. Lebow , Richard Ned , “ Windows of Opportunity: Do States Jump Through Them? ” International Security 9 ( Summer 1984 ), pp. 147 –86 CrossRef Google Scholar .

73. See Bundy , McGeorge , Danger and Survival: Choices About the Bomb in the First Fifty Years ( New York : Random House , 1988 ) Google Scholar ; John Lewis Gaddis, The Long Peace ; Lebow , Richard Ned and Stein , Janice Gross , We All Lost the Cold War ( Princeton, N.J. : Princeton University Press , 1994 ) Google Scholar .

74. Waltz writes that “Rules, institutions, and patterns of cooperation, when they develop in self-help systems, are all limited in extent and modified from what they might otherwise be.” See “Reflections on Theory of International Politics ,” p. 336.

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• Volume 48, Issue 2
• Richard Ned Lebow (a1)
• DOI: https://doi.org/10.1017/S0020818300028186

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The Decline of War Since 1950: New Evidence

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• First Online: 15 November 2019

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• Michael Spagat 3 &
• Stijn van Weezel 4  

Part of the book series: Pioneers in Arts, Humanities, Science, Engineering, Practice ((PAHSEP,volume 27))

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For the past 70 years, there has been a downward trend in war sizes, but the idea of an enduring ‘long peace’ remains controversial. Some recent contributions suggest that observed war patterns, including the long peace, could have resulted from a long-standing and unchanging war-generating process, an idea rooted in Lewis F Richardson’s pioneering work on war. Focusing on the hypothesis that the war sizes after the Second World War are generated by the same mechanism that generated war sizes before the Second World War, recent work failed to reject this ‘no-change’ hypothesis. In this chapter, we transform the war-size data into units of battle deaths per 100,000 of world population rather than absolute battle deaths – units appropriate for investigating the probability that a random person will die in a war. This change tilts the evidence towards rejecting no-change hypotheses. We also show that sliding the candidate break point slightly forward in time, to 1950 rather than 1945, leads us further down the path toward formal rejection of a large number of no-change hypotheses. We expand the range of wars considered to include not just inter-state wars, as is commonly done, but also intra-state wars. Now we do formally reject many versions of the no-change hypothesis. Finally, we show that our results do not depend on the choice of war dataset.

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Studying micro dynamics in civil wars: introduction

Have wars and violence declined?

Could humanitarian intervention fuel the conflict instead of ending it, 11.1 a continuing debate.

The possibility that war might be in decline has long tantalized academics and the general public. Ongoing debate has focused on whether there might be a secular downward trend in war sizes which might herald the decline of war. For roughly 70 years there has not been a truly huge war or a direct confrontation between major powers. Nevertheless, the idea of an enduring ‘long peace’, in the coinage of Gaddis ( 1986 ), remains controversial. Some scholars have developed a decline-of-war thesis in some detail (Goldstein, 2011 ; Pinker, 2011 ; Hathaway & Shapiro, 2017 ) while others reject it (Braumoeller, 2013 ; Cirillo & Taleb, 2016b ; Clauset, 2018 , 2020 ). Here we do not attempt a broad survey of the existing literature. Rather, we focus on the recent contributions of Cirillo & Taleb ( 2016b ) & Clauset ( 2018 , 2020 in this volume) suggesting that observed war patterns, including the long peace, could have come from a long-standing and unchanging war-generating process. In particular, we engage with Clauset ( 2018 ) who tests the hypothesis that the war sizes after the Second World War are generated by the same mechanism that generated war sizes before the Second World War. He fails to reject what we will call a ‘no-change hypothesis’.

Here are the main contributions of our chapter. First, we give a simple exposition of the central ideas behind the new critiques of the decline-of-war thesis made by Cirillo & Taleb ( 2016b ) and Clauset ( 2018 , 2020 ). These ideas hinge centrally on the original insight of Richardson ( 1948 , 1960 ) into the fat-tailed size distribution of modern wars. Second, we transform the war-size data into units of battle deaths per 100,000 of world population rather than absolute battle deaths and argue that these units are appropriate for investigating the probability that a random person will die in a war. We show that this change tilts the evidence towards rejecting a large number of no-change hypotheses. Third, we show that sliding the candidate break point slightly forward in time, to 1950 rather than 1945, leads us further down the path toward formal rejection of a range of no-change hypotheses. Finally, we expand the types of wars to include intra-state as well as inter-state. Now we almost always formally reject our no-change hypotheses. Footnote 1 Finally, we show that our results do not depend on the choice between two widely used war datasets.

11.2 Richardson Provides Our Framework

Decades ago, Richardson ( 1948 ) introduced the idea that war sizes tend to follow what is known as a power law distribution. Footnote 2 Technically, this means that the frequency of wars of size x is proportional to \( x^{ - \alpha } \) where \( \alpha > 1 \) is some constant. Thus, bigger wars are less common than smaller ones with the value of \( \alpha \) governing the rate at which war frequencies decrease as war sizes increase. This remarkable insight has fared well against more than half a century of new data and the development of more rigorous statistical methods for estimating and testing power laws (Cederman, 2003 ; Clauset, 2018 ; González-Val, 2016 ).

For our purpose, the important characteristic of power-law distributions is that they have what are known as ‘fat upper tails’ governing the relationship between war sizes and their frequencies. This property entails that, although bigger wars are less common than smaller ones, the rate at which war frequencies decline with war sizes is much slower than would be the case if war sizes followed a common normal, or ‘Bell Curve’, distribution. Most people are conditioned to think in terms of Bell Curves, so some mental effort is required to adjust to fat tails. Here is the most salient point to bear in mind in the present context; huge wars are really rare but not really really really, rare.

We illustrate the key fat-tail property with the following numerical example. Suppose that every time the world experiences a new war, w , the probability that the war size will grow to at least the size of the First World War, \( \bar{w} \) – hereafter a ‘truly huge war’ – is 0.006. Footnote 3 We now make the important assumption that war-size realizations are statistically independent of each other, which implies that the size of war w tells us nothing about the sizes of previous or future wars. Under these conditions, the chance that there is at least one truly huge war after 200 war-size realizations is roughly 2/3. Footnote 4 If we lower the probability that each new war will turn out to be a truly huge one down from 0.006 down to \( P\left( {w \ge \bar{w}} \right) = 0.0001 \) , then the chance of at least one truly huge war in 200 draws drops to around 1 in 50. Decreasing the probability of a truly huge war on each draw even further down to \( P\left( {w \ge \bar{w}} \right) = 10^{ - 7} \) , decreases this chance all the way down to about 1 in 50,000. Thus, it makes a big practical difference whether truly huge wars are really rare, \( P\left( {w \ge \bar{w}} \right) = 0.006 \) ; really really rare, \( P\left( {w \ge \bar{w}} \right) = 0.0001 \) ; or really really really rare, \( P\left( {w \ge \bar{w}} \right) = 10^{ - 7} \) .

This fat-tail property of the war-size distribution potentially places the world into what we might call a ‘bad Goldilocks’ range. On the one hand, 0.006 is large enough that we might expect to suffer a truly huge war once every few generations, far too often for such a calamity. On the other hand, 0.006 is small enough that the risk of a truly huge war can lurk below the surface for a long time without being exposed as a major threat. This is evident within our example according to which the world has about a 1/3 chance of experiencing 200 wars without suffering a truly huge one. And if our luck holds out this long, we could easily last another 200 wars without suffering a truly huge war.

Thus, we arrive at an important insight flowing from the pioneering work of Richardson ( 1948 ) and developed further by Clauset ( 2018 ); the threat of a truly huge future war can be quite serious while simultaneously remaining well-hidden for a long time. In other words, we should not dismiss the possibility of a truly huge future war just because such an event would be dramatically out of line with our range of experience over the last 70 years. At the same time, we must not imprison ourselves in our own ahistorical assumptions that rely on the artifice of independent draws with fixed and unchanging probabilities. These calculations are helpful to understand important concepts and establish baseline expectations. But they do not possess any special powers to describe the world we currently live in or to predict its future. A finding that the war-size pattern of recent decades is consistent with an unchanging war generation mechanism over the last two centuries does not prove that that such a mechanism actually exists.

11.3 A New Debate on the Decline of War

There is diversity of opinion among proponents of the decline-of-war thesis. First, it is standard to claim that the absolute level of war violence has declined over time, albeit unevenly (Lacina & Gleditsch, 2005 ; Human Security Report Project, 2011 ). Different scholars emphasize different time periods, although most view the Second World War as an important turning point. Second, sometimes the main claim is about per capita, rather than total, war violence (Pinker, 2011 ). A third tendency is that no one we are aware of argues that truly huge wars have become impossible. To be sure, a sense of optimism pervades this literature with proponents generally providing reasons why war violence is decreasing and why this trend might reasonably be expected to continue. Yet, invariably, there is also a note of caution about the future.

The recent critique of the decline-of-war thesis was instigated by Cirillo & Taleb ( 2016b ), who collected data on 565 wars going all the way back to Boudicca’s rebellion against the Romans in the first century common era (CE). Using extreme value theory to fit the fat-tailed data, they find that they cannot reject their model and conclude from this non-rejection that the data do not support a decline-of-war thesis. In a companion paper they go further, writing that ‘there is no scientific basis for narratives about change in risk’ (Cirillo & Taleb, 2016a ).

Cirillo & Taleb ( 2016b ) helped to prompt renewed focus on the importance of fat tails in war sizes for the decline-of-war debate; however, they left several important issues unresolved. First, although a main contribution of their work is the data collection effort, their dataset is not publicly available, and they have refused to allow other researchers to examine it (Spagat, 2017 ). This stance takes their work outside the scientific universe, at least for now. Second, non-rejection of a model fitting two thousand years of data does not rule out the possibility of scientifically grounded discussions about possible changes in war risks during subsets of these two thousand years. For example, there could be a big change after, e.g., war number 500 but without the last 65 draws disturbing the fit of the first 500 draws sufficiently to lead to rejection of the whole model. Imagine flipping a coin that has a 0.5 probability of landing heads for the first 500 flips and a 0.3 probability of landing heads for the last 65. You would probably not reject a hypothesis that all the flips had a chance pretty close to 0.5 of landing heads. More importantly, if you confine your analysis to the 565 flips as a whole, then you will get no hint that there was a dramatic change after flip number 500. It would have been more appropriate to test for a break in the data at a potential change point, such as the end of the Second World War; Cirillo & Taleb ( 2016b ) do not provide such a test. Third, there is an overarching assumption in this approach that the only evidence scientifically admissible to our discussion is a list of war sizes and timings. Cirillo & Taleb ( 2016b ) seem to think that historical events such as peace treaties, formation of international institutions or social trends such as improving human rights are, simply, outside the bounds of a scientific discussion; this restrictive view makes little sense.

Clauset ( 2018 ) addresses the first two of the unresolved issues. First, he uses the open-source Correlates of War (COW) dataset that covers interstate wars from the beginning of the 19th century to the present (2007). Second, his whole analysis focuses on testing for a trend break starting at the end of the Second World War. The essence of his approach on war sizes is to fit a power law to the data up through the Second World War and then test the hypothesis that the data after 1945 was generated by this distribution, i.e., he tests what we call a no-change hypothesis. Clauset ( 2018 ) concludes that he cannot reject the no-change hypothesis. This finding is intuitive in light the numerical examples provided above although there is certainly tension between the no-change hypothesis and the last 70 years.

Clauset ( 2018 ) provides a useful contribution to our thinking but, at the same time, we must be cautious about this result for several reasons. First, other information besides the time series of war sizes is potentially relevant. Second, we should not think exclusively in terms of any one particular hypothesis such as the no-change one. There are other hypotheses, more in line with a decline-of-war thesis, that would also not be rejected by the data. For example, suppose we modify the no-change hypothesis by stipulating that wars with more than 5 million battle deaths became very very rare after the Second World War. That is, we virtually eliminate the fat tail from the hypothesized war generation mechanism. This restriction is fully consistent with the post-1945 experience since no war during this period comes close to such a size. Thus, this hypothesis is consistent with decline-of-war ideas and will also not get rejected by the data. And there is no reason to privilege the no-change hypothesis over this one. Third, we must not fall into the trap of accepting the null hypothesis based on its non-rejection. Clauset ( 2018 ) finds that we would finally reject his no-change hypothesis ( \( p < 0.05 \) ) after about 100–140 more years without a truly huge war. Even then we still would not be able to entirely rule out the no-change hypothesis. However, if the data became extremely contrary to the no-change hypothesis after 100 sufficiently peaceful years then the data would already be fairly contrary to this hypothesis after 50 sufficiently peaceful years. Returning to our earlier calculations, recall that the Gleditsch ( 2004 ) dataset contains 212 wars for the period after the Second World War. If a further 212 wars occur without a truly huge one, perhaps over the next 70 years, we could then reject this version of the no-change hypothesis at a 10% level, which would be rather convincing evidence that there was a change for the better. In other words, the 0.05 threshold is arbitrary and excessively binary; non-rejection of the no-change hypothesis does not mean that the decline-of-war thesis is false until it suddenly switches to true after 100 years without a truly huge war.

11.4 Measuring War

Our empirical analysis relies on two datasets that cover war sizes and dates; the commonly used Correlates of War (COW) dataset (Sarkees & Wayman, 2010 ), which was also used by Clauset ( 2018 ), and the dataset compiled by Gleditsch ( 2004 ). The two datasets overlap substantially, and both cover the period 1816–2007. Indeed, the Gleditsch ( 2004 ) dataset is based on the COW dataset. However, there are important distinctions that are worth understanding even though it turns out that our results do not depend materially on the choice of dataset. For COW there is a big change in the inclusion criteria in 1920 with the founding of the League of Nations. The fundamental test for COW is always membership in the international system for both states, in the case of inter-state war, and for the state in the case of intra-state war. Between 1816 and 1920 this test breaks down into two parts; (i) a population greater than 500,000 and (ii) being ‘sufficiently unencumbered by legal, military, economic, or political constraints to exercise a fair degree of sovereignty and independence’. After 1920, the COW test switches to membership in the League of Nations (or United Nations) and receiving diplomatic missions from any two major powers (Singer & Small, 1972 ). Gleditsch & Ward ( 1999 ) note that, in practice, the pre-1920 test boils down to having formal diplomatic relations with Britain and France. This rule excludes many countries and their wars, including the three Anglo-Afghan wars that took place between 1839 and 1919 and some intrastate wars such as the 1831–45 civil war in Central America.

It would be unfair to label the COW dataset as simply incorrect, yet we believe that its British-French emphasis excludes many wars that are relevant to the decline-of-war debate. The revised data by Gleditsch ( 2004 ), which corrects these systematic problems, contains 574 wars between 1816 and 2007, 136 of which are interstate wars. During the same period COW contains only 474 wars, 95 of which are interstate. Thus, the difference in war counts is substantial. Moreover, 1920 is close enough to the Second World War so that the 1920 switch could potentially affect the results of Clauset ( 2018 ). Thus, we prefer the Gleditsch data but run our calculations on both datasets. Footnote 5

Our second departure from Clauset ( 2018 ) is that we divide all war sizes by world population estimates. These are applied to the start year of each war and taken from Fink-Jensen ( 2015 ), Klein Goldewijk et al. ( 2010 ), and UN ( 2013 ) with some interpolations before 1950. The probability that an average person will be killed in war is of particular interest to the decline-of-war discussion and population adjustment is appropriate to assess this probability. In a similar vein, analysts normally assess, for instance, violence progress by examining the number of homicides per 100,000 of population or the quality of health services through the number of maternal deaths per 1000 live births. At the same time, we recognize the point of Braumoeller ( 2013 ) who argues that examination of unadjusted war sizes is of great relevance to understanding human war-proneness. Footnote 6

A third contrast with Clauset ( 2018 ) is that we include in our analysis all the wars in each dataset, not just interstate wars. Footnote 7 We think that there is no a priori theoretical justification to separate out interstate wars and agree with Small & Singer ( 1982 ) who argued that ‘an understanding of international war cannot rest on interstate wars alone’. The common focus on wars involving major powers or other interstate wars seems to be driven by data availability rather than theoretical considerations (Cunningham & Lemke, 2013 ). Indeed, the third, fourth and sixth largest wars measured in per capita terms in the Gleditsch dataset are all intra-state (Fig.  11.1 ). Thus, combining all wars is best practice in our view although we also run our calculations on interstate wars alone.

Based on Gleditsch ( 2004 )

The largest wars as measured by battle deaths per 100,000 on the right \( \varvec{y} \) axis.

War-size numbers are intended to include just battle deaths, but both of our datasets work from available sources that sometimes mix in other kinds of deaths. This issue creates two separate problems. First, ideally we would have data on the full human cost of war but often we only have data on the battle-death component of this cost. For example, both datasets record 910,084 deaths for the Korean War, but a full figure would include famine deaths that could push the number up to 5 or 6 million (Lacina et al., 2006 ). Second, there is inconsistency across wars since some figures hue close to a battle-deaths-only concept whereas other figures are more comprehensive.

11.5 Insights from the Data

A particular feature of our approach is the large number of no-change hypotheses that we test. All our hypotheses are based on two separate cut-off points: one for time periods and the other for per capita war sizes. Our time periods pivot around either the Second World War or the Korean War, but future work should consider more cut-off points. For war sizes we consider all possible cut-offs and examine the fraction of all wars above each war-size cut-off for both the early period and the late period. In short, we examine many right-hand tails and test whether the tails for the later periods are thinner than the tails for the earlier periods.

Here are some sample calculations when the time cut-off point is 1945. According to the Gleditsch ( 2004 ) data, there were 362 wars between 1816 and 1945 with the Second World War being by far the largest. Our first no-change hypothesis for the post-1945 period is that the probability that a random war after 1945 will kill at least 781 people per 100,000 (Fig.  11.1 ) is given by the fraction of all wars before 1945 that reached this violence level. This fraction is \( p_{0} = \frac{1}{362} \approx 0.003 \) .

Zero wars out of 212 in the Gleditsch ( 2004 ) data attained this size between 1946 and 2007. If war sizes are drawn randomly and independently of each other and if the no-change hypothesis is true, then the probability of this happening is \( (1 - \frac{1}{362})^{212} = 0.56 \) . This probability can be interpreted as a p -value on one particular no-change hypothesis at the most extreme end of the distribution of war sizes. Footnote 8

Next we calculate exactly the same types of p -values but for lower and lower war sizes. For war sizes beginning at 781 per 100,000 and moving down towards 499 per 100,000, the size of the First World War, the p -values stay constant. At 499 battle deaths per 100,000 the p -value drops to \( (1 - \frac{2}{362})^{212} = 0.31 \) . It then stays constant all the way down to 52 battle deaths per 100,000, the size of the American Civil War (1861–65), where the p -value drops down to 0.17 − \( (359/362)^{212} \) . In short, the three biggest wars were all before World War II inclusive and together they yield a preponderance of evidence against a no-change hypothesis but not a formal rejection at the 0.05 level. The next largest war is the second phase of the Chinese Civil War which pitted the communists under Mao Zedong against the nationalists under Chiang Kai-shek and caused 51 battle deaths per 100,000 people. The no-change hypothesis assigns probability \( \frac{3}{362} \) to the probability that each war size after World War II will exceed 51. This happens once in 212 draws so the p -value on the no-change hypothesis adds together the probability of 0 wars above size 51 and the probability of 1 war above size 51, leading to a p -value of 0.47.

We calculate p -values similarly as we move to smaller and smaller war sizes. When, for example, there are 6 wars before 1945 of size s and above then the no-change hypothesis fixes a probability of \( \frac{6}{362} \) on the event that a new post-1945 war will be of size s or above. When, for example, three out of these 212 wars after 1945 are above size s then the p -value on the no-change hypothesis is the probability of three or fewer wars of size s or greater after 212 independent draws, each with probability \( \frac{6}{362} \) of reaching this size. We use the binomial formula to make this calculation. Footnote 9

Panel (a) in Fig.  11.2 displays the p -values for the tests of all no-change hypotheses tests with cut-offs for war sizes below 50 battle deaths per 100,000 and with a time break point of 1945. Reading from right to left the curve dips down below 0.2 as we move through the Third Sino-Japanese War which began in 1937, Footnote 10 the Russian Civil War (1918–20) following the Russian Revolution of 1917, and the 1864 Muslim revolt in Xinjiang, China. The p -values then rise back above 0.8 because the next four largest wars all occurred after the Second World War. These are the Korean War (1950–53), the second phase of the Vietnam War which started in 1965, the Iran-Iraq war between 1980 and 1988, and finally the Second South Sudan War (1983–2005). Next, continuing to read from right to left, the next 9 wars all took place before the Second World War, bringing the p -values back down to around 0.2.

Tests of no-change hypotheses for all wars. Based on Gleditsch ( 2004 ), using 1945 ( a ) and 1950 ( b ) as break points

The evidence in Fig.  11.2 is unfavorable to the no-change hypothesis \( (p < 0.5) \) except in a narrow range of tails for war sizes between about 25 and 28 per 100,000. At the same time, we never reject the no-change hypothesis at the standard 0.05 level. The evidence leans towards the decline of war idea but is far from definitive.

When we use 1950, rather than 1945, as a break point the results are much more favourable to the decline-of-war thesis. Now the eight largest wars in per capita terms all occur before the break point. Panel (b) displays the new p -values. No-change hypotheses are often rejected at 0.05, and even 0.01 levels for a wide range of tails. Two of the very biggest wars (the Chinese Civil War and the Korean War) broke out within the 1945–50 time window so the p -value curve now drops much lower than it did when 1945 was break point. Footnote 11

We have made four separate data changes compared to Clauset ( 2018 ): measuring war sizes in per capita terms, using Gleditsch data rather than COW data, considering 1950 as a break point and including intrastate as well as interstate wars. To isolate the importance of each particular change we now consider them in turn. We first note that adjusting for world population levels is essential to get anything resembling the results in this chapter. This is so much true that we do not even bother showing pictures unadjusted for population. Second, the choice of COW or the Gleditsch war data does not matter much (Fig.  11.3 ). Third, both Figs.  11.2 and 11.3 show that the choice of break point does matter; evidence against the no-change hypothesis is much stronger when the break is at 1950 than it is when the break point is 1945. Finally, Figs.  11.4 and 11.5 show that our decision to include intrastate wars also matters. We think this is simply due to sample size; excluding intrastate wars decreases the number of wars, making it harder to reject the no-change hypothesis.

Tests of no-change hypotheses for all wars. Based on COW data, using 1945 ( a ) and 1950 ( b ) as break points

Tests of no-change hypotheses for interstate wars only. Based on Gleditsch ( 2004 ), using 1945 ( a ) and 1950 ( b ) as break points

Tests of no-change hypotheses for interstate wars only. Based on COW data, using 1945 ( a ) and 1950 ( b ) as break points

11.6 A More Peaceful World Since 1950

There will continue to be debate on the probability of another truly huge war. If we limit our attention to the probability of a future war at least as large as the First World War then, consistent with Clauset ( 2018 ), our analysis suggests that there is presently not enough data to draw a strong conclusion. At the same time, our analysis also suggests that the chances of drawing a truly huge war are probably lower now than they were in the 19th century and the first half of the 20th century. When we widen our scope to include smaller but still very large wars, e.g., wars killing more than 40 per 100,000 of world population then there is substantial evidence that the world has become more peaceful since the 1950s.

Until recently scholars have tended to assume that the Second World War is the obvious candidate for a break point into a more peaceful world. However, recent papers by Fagan et al. ( 2018 ) and Cunen et al. ( 2018 ) start from an agnostic position on potential break points and use statistical methods to detect convincing ones. Both papers find substantial evidence for a change at 1950 although they identify other candidate break points including 1912 (Fagan et al., 2018 ) and 1965 (Cunen et al., 2018 ). These results complement ours nicely.

There is certainly room to improve our analysis. First, we repeat our caution that a full treatment of the issues should consider more than just the time series of war sizes (and population numbers). Second, it would be helpful to go beyond battle deaths to include more complete numbers on war deaths. Unfortunately, it is unlikely that this second hope will ever be fully possible. Third, the new research into defining change points is an important development that will, hopefully, continue. Despite the potential for improvement, we believe that our chapter should shift the debate in favour of the decline-of-war thesis.

Our findings do not refute those of Clauset ( 2018 ). It can be true simultaneously that per capita war sizes decrease while the absolute war size generation mechanism does not change.

Spagat ( 2015 ) provides a non-technical introduction to power laws.

This probability is not entirely fictitious. In the dataset compiled by Gleditsch ( 2004 ), the First and Second World Wars are by far the biggest two out of 362 wars that occurred between the beginning of the 19th century and 1945: \( 2/362 \approx 0.006 \) .

\( 1 - \left( {1 - 0.006} \right)^{200} \approx 0.7 \) .

The Gleditsch ( 2004 ) dataset covers about two centuries of war yet contains roughly the same number of wars as the Cirillo & Taleb ( 2016b ) dataset which covers two millennia of wars. The inclusion criteria for the two datasets seem to be similar.

A war that kills one million people is an unmitigated disaster both in a world of 5 billion people and in a world of 9 billion people.

For COW, all wars means inter-state, intra-state, extra-systemic and non-state. The Gleditsch dataset does not have the last two of these categories, although its more inclusive definition of state means that it codes some COW extra-systemic and non-state wars as either inter-state or intra-state wars. Arguably, we should subtract the populations of ungoverned spaces that fall outside the scope of the Gleditsch dataset from our world population figures. Such adjustments would enhance our decline-of-war results because they would increase the per capita sizes of earlier wars relative to later ones; governance spreads over time. However, these adjustments would be very hard to perform with any degree of accuracy, so we do not attempt them here.

Braumoeller ( 2013 ) offers a similar calculation.

For simplicity, we specify our no-change hypotheses as single probabilities rather than as uncertain ranges of probabilities, although we plan to relax this assumption in future research.

This war is often known as the Second Sino-Japanese War. The data counts three wars between China and Japan: the first starting in 1894, the second in 1931, and the third in 1937.

We date wars by when they start.

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Spagat, M., van Weezel, S. (2020). The Decline of War Since 1950: New Evidence. In: Gleditsch, N.P. (eds) Lewis Fry Richardson: His Intellectual Legacy and Influence in the Social Sciences. Pioneers in Arts, Humanities, Science, Engineering, Practice, vol 27. Springer, Cham. https://doi.org/10.1007/978-3-030-31589-4_11

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Explaining the Long Peace: Why von Neumann (and Schelling) Got It Wrong

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Frank C Zagare, Explaining the Long Peace: Why von Neumann (and Schelling) Got It Wrong, International Studies Review , Volume 20, Issue 3, September 2018, Pages 422–437, https://doi.org/10.1093/isr/vix057

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Alexander J. Field (2014, 54) argues that game theory “offers little guidance, normatively or predictively, in thinking about behavior or strategy in a world of potential conflict.” He makes this claim by attributing to John von Neumann a view of the superpower relationship during the Cold War period that has no basis in fact and inferring policy prescriptions to that view that are simply not there. Field also suggests that Thomas Schelling's explanation of the “event that didn't occur” leads to the conclusion that “deterrence works because we are human, not because we are entirely rational” (Field 2014, 86). In this essay I show that there is at least one logically consistent game-theoretic explanation of the absence of a nuclear war during the long-peace of the 1950s and early 1960s. I also demonstrate that Field's assumptions lead to exactly the opposite conclusions; that is, that mutual deterrence can in fact be reconciled with rationality and that game theory is a powerful tool for understanding interstate conflict.

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Nothing unusual about 'the long peace' since WWII

Since the end of World War II, few violent conflicts have erupted between major powers. Scholars have come to call this 73-year period “the long peace.” But is this stretch of relative calm truly unusual in modern human history – and evidence that peace-keeping efforts are working? Or is it a cyclical peace, destined to be broken, with few lessons for preventing interstate conflict?

A new analysis by  Aaron Clauset , an assistant professor of computer science at the University of Colorado at Boulder and the BioFrontiers Institute and an external faculty member of the Santa Fe Institute, aims to answer that long-standing question using novel statistical techniques to tease out how the “long peace” stacks up against historical trends of calm and conflict.

“There’s been a debate among people who think about conflict and war, policymakers and researchers, whether or not the pattern since World War II represents a trend,” Clauset says. Resolving this debate “is important because it shapes how we think about peace,” he adds.

Determining whether we are truly in the midst of a prolonged period of peace can help us understand what is an effective deterrent to war and what is not. If this really is a “long peace,” we can then examine why — and identify the mechanisms that have contributed to that peace. But if it’s not an anomaly, we may need to use caution in ascribing the current calm to particular policies or actions.

Using data on interstate conflicts worldwide between 1823 and 2003, Clauset looked for trends in the magnitude of those conflicts and the years between them, and then used that information to create models to determine the plausibility of a trend toward peace since World War II.  “The tools, the framework and the models we built in this paper haven’t been used before, and they allow us to distinguish trends from fluctuations,” Clauset says.

What he found is that this prolonged period of peace is not so unusual. “The results of the study are that at least statistically speaking, the efforts to create peace have not changed the frequency of war,” Clauset says. “These periods of peace are relatively common. It doesn’t appear that the rules that generate war have changed.”

Between 1823 and 1939, there were 19 large wars, and a major conflict occurred about every 6.2 years. Then came an especially violent period: Between 1914 and 1939, which encompasses the onsets of the first and second world wars, 10 large wars erupted — about one every 2.7 years. In contrast, during the long peace of the 1940–2003 post-war period, there were only 5 large wars — about one every 12.8 years. So essentially, the long peace “has simply balanced the books,” counterbalancing the “great violence” of the early to mid 20th century, Clauset writes.

That’s not to say, however, that the current calm is insignificant. “This fact does not detract from the importance of the long peace, or the proposed mechanisms that explain it,” such as the spread of democracy and international diplomacy, he writes in the paper. “However, the models indicate that the post-war pattern of peace would need to endure at least another 100–140 years to become a statistically significant trend.”

Clauset compares this to flipping a coin over a period of time. “If I’m seeing a low number of heads out into the future, how long will the coins need to flip before the pattern really looks different? At what point does this pattern start to look unusual?”

Clauset says he is hopeful that the study will encourage a rethink of “the long peace.”

“I hope it will encourage caution,” Clauset says. “It’s a worthwhile exercise to check our assumptions about whether there’s a real trend or not.”

Part of the reason we tend to overstate the significance of the lack of major interstate conflict since World War II may be because of a human tendency to overestimate our ability to understand complexity, he notes in the paper.  “Human agency certainly plays a critical role in shaping shorter-term dynamics and specific events in the history of interstate wars,” he writes. “But, the distributed and changing nature of the international system evidently moderates the impact that individuals or coalitions can have on longer-term and larger-scale system dynamics.

The research was supported by the One Earth Future Foundation, whose mission is to catalyze systems that eliminate the root causes of war.

Read the paper, “ Trends and Fluctuations in the Severity of Interstate Wars ," in  Science Advances   (February 21, 2018)

Read the article, " Are we in the middle of a long peace—or on the brink of a major war? " in  Science  (February 21, 2018)

Read the article, " War may be closer than we think ," in  Pacific Standard   (February 23, 2018)