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The theory of war cycles holds that wars happen in cycles.
The cycles of war 
The forerunner of the study of war cycles was Edward R Dewey, with Quincy Wright's monumental A Study of War adding impetus to the discipline. The credibility of the study of cycles was frequently questioned, as this type of inquiry attracts persons with marginal credibility and interest in paranormal issues. However, with advent of computer algorithms minimizing the dampening effect affecting the abstracted oscillations and facilitating the detection of stochastic drifts, the study of cycles is subject to renewed interest (see, e.g., *History & Mathematics: Historical Dynamics and Development of Complex Societies / Ed. by Peter Turchin et al.. Moscow: KomKniga, 2006. ISBN 5-484-01002-0).
Inflection points of war cycles 
Fig. 1. Frequency and intensityPsychological Reports, 83, 139–143).
of Western Wars (1600–1945). The 1618–1648 interval marks the Thirty Years' War, the 1789–1815 interval marks the Wars of the French revolution and the Napoleonic Wars, and the 1914–1945 interval marks World Wars I and II. (From Krus, D.J., Nelsen, E.A. & Webb, J.M. (1998) "Recurrence of war in classical East and West civilizations".
Fig. 2. Frequency and intensityPsychological Reports, 83, 139–143).
of Chinese Wars (200 BCE–1945). The 220–618 interval marks the "Period of Disunion" (Chinese Dark Ages), during which the Confucian teachings were abandoned. The most intense conflict in recorded history was the Second World War, and both graphs are plotted relative to that conflict. (From Krus, D.J., Nelsen, E.A. & Webb, J.M. (1998) "Recurrence of war in classical East and West civilizations".
In the judgment of the Nuremberg Tribunal, war of aggression is the supreme crime, and there is hardly any other issue that is more relevant to the social sciences than the study of the decision-making process when a person or a group of persons decides that another group of people must face death. Historians speculated about this decision-making process for centuries without reaching consensus, as wars are complex phenomena with multiple determinants. The decision to initiate a war marks an inflection point of the war-peace cycle, and the decision to cease hostilities marks the end of a particular cycle. Comparative studies of war cycles can contribute to explication of facets of this decision-making process. Most relevant of these facets are those that help us to identify the preventable factors influencing the decision to initiate (and to terminate) a war.
Comparative studies 
Quantitative studies of bellicosity of the Western civilization and the Confucian civilization of the East was pioneered by Lewis Fry Richardson. Richardson's studies led him to the conclusion that "Confucian-Taoist-Buddhist religion of China stands out conspicuously as being either itself a pacifier, or else associated with one" and that "it seems probable that the comparative peacefulness of China prior to 1911 was the result of instruction, and in particular of Confucian instruction."
Richardson's findings were based on data spanning about a century. Study by Krus, Nelsen, & Webb (1998) lengthened his perspective for the wars of the Western civilization by about three centuries (Fig. 1) and for the Eastern Civilization by about 17 centuries (Fig. 2). In Fig. 2, the 220–618 time interval corresponds to the period in Chinese history called the Period of Disunion (also called the Chinese Dark Ages or six dynasties), when Confucius' teachings were abandoned. Krus et al. (1998) concluded that "In the Empire of China, when the Confucian philosophy was predominant, the peace lasted significantly longer than in the West. When Confucian teachings were abandoned, the frequency of warfare approximated that observed for the Western countries."
For another comparative study that specifies a mathematical model of war cycles and tests it cross-culturally and cross-historically see Secular Cycles and Millennial Trends. Note that this study tries to connect the war cycles with long-term trend dynamics.
See also 
- Dewey, E.R. (1951) "The 57-year cycle in international conflict". Cycles 2, 1, 4–6.
- Dewey, E.R. (1952) "The 142-year cycle in war". Cycles 3, 6, 201–204.
- Dewey, E.R. (1967) "Systematic Reconnaissance of Cycles in War". Cycles, January 1967. (Request reprint).
- Ellis, M.H. (1997) Unholy alliance: religion and atrocity in our time. Minneapolis: Fortress Press.
- Korotayev, A., Malkov, A., & Khaltourina, D. (2006) Introduction to Social Macrodynamics: Secular Cycles and Millennial Trends. Moscow: URSS. ISBN 5-484-00559-0.
- Korotayev, A. & Khaltourina D. (2006) Introduction to Social Macrodynamics: Secular Cycles and Millennial Trends in Africa. Moscow: URSS. ISBN 5-484-00560-4.
- Krus, D. J. & Blackman, H. S. (1980) "Time scale factor as related to theories of societal change". Psychological Reports 46, 95–102. (Request reprint).
- Krus, D.J., & Ko, H.O. (1983) "Algorithm for autocorrelation analysis of secular trends". Educational and Psychological Measurement 43, 821–828. (Request reprint).
- Turchin, P., et al., eds. (2007) History & Mathematics: Historical Dynamics and Development of Complex Societies. Moscow: KomKniga/URSS. ISBN 5-484-01002-0.
Primary sources 
- McMaster, Jr., R. E. (1978). Cycles of War: The next six years.
- Krus, D.J., Nelsen, E.A. & Webb, J.M. (1998) "Recurrence of war in classical East and West civilizations". Psychological Reports 83, 139–143 (Request reprint).
- Krus, D. J. & Webb, J. M. (2001) "Für oder gegen ein militarisches Eingreifen: Ist die Einstellung zum Krieg eine Variable der Gesinnung oder des sitationsbedingten Gemütszustands?" Zeitschrift fur Sozialpsychologie und Gruppendynamik in Wirtschaft und Gesellschaft 26.Jg. Heft 2, 3–8 (Request reprint in English, in German).
- Richardson, L.F. (1960) Statistics of deadly quarrels. Pacific Grove, CA: Boxwood Press.
- Turchin, P. (2006) War and Peace and War: The Life Cycles of Imperial Nations. Pi Press.
- Wright, Q. (1965) A study of war (2nd ed.). Chicago: University of Chicago Press.
External links