War cycles
The word “cycle” (from Greek κυκλος) is used here in a temporal sense to describe the recurrence of social events which happen with far less regularity than the recurrence of natural events (as e.g., the cycles of seasons.) 
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.

The cycles of war
In the judgment of the Nuremberg Tribunal, war of aggression is the supreme crime and there is hardly other issue that is more relevant to the social science than the study of the decision-making process when a person or a group of persons decide that another group of people must inflict death and 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.
 

Fig. 1. Wars of the Western Countries (1600 - 1945). 1618-1648 interval marks the Thirty Years' War 1789-1815 interval marks the Napoleonic Wars, 1914-1945 interval marks the World War I and II.

Fig. 2. Wars of the China (200 BCE - 1945). The 220-618 interval marks the Period of Disunion" (Chinese Dark Ages) during which the Confucian teachings were abandoned.

Comparative studies
Quantitative studies of bellicosity of the Western civilization and Confucian civilization of the East was pioneered by Lewis Fry Richardson. Richardson studies led him to 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 3 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), 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."
 
Ethical canons
Pacific ethics of the Western civilization are based to a degree on ethical teachings of monotheistic religions. These religious canons are quite effective in preventing violence by individuals, but less successful in preventing the collective violence. Results of the comparative studies of the war cycles support Richardson's observations of the relative peacefulness of China prior to 1911. Richardson asks the question: "If China could thus be made peaceable by Confucian instruction in pacific ethics, why not the whole world?" Experience of a large segment of humanity over a time interval spanning millennia indicates that a peaceful civilization can exist without subscribing to religious precepts and that a secular ethic system, epitomized by that of Confucius, is likely one of the factors lessening the probability of a decision to initiate a war.
 
References
· 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. 
· Krus, D. J. & Blackman, H. S. (1980) Time scale factor as related to theories of societal change. Psychological Reports, 46, 95-102.
· Krus, D.J., & Ko, H.O. (1983) Algorithm for autocorrelation analysis of secular trends. Educational and Psychological Measurement, 43, 821-828.
· Krus, D.J., Nelsen, E.A. & Webb, J.M. (1998) Recurrence of war in classical East and West civilizations. Psychological Reports, 83, 139-143.
· Richardson, L.F. (1960) Statistics of deadly quarrels. Pacific Grove, CA: Boxwood Press.
· Wright, Q. (1965) A study of war. (2nd Ed.). Chicago: University of Chicago Press.
 

See also
Cycle de la guerre