Editing War (section)

===Political science===
The statistical analysis of war was pioneered by [[Lewis Fry Richardson]] following [[World War I]]. More recent databases of wars and armed conflict have been assembled by the [[Correlates of War]] Project, Peter Brecke and the [[Uppsala Conflict Data Program]].<ref name="UCDP">{{Cite web|url=https://www.pcr.uu.se/research/ucdp/about-ucdp/|title=Uppsala Conflict Data Program – About|access-date=2019-04-09|archive-url=https://web.archive.org/web/20190403211437/http://pcr.uu.se/research/ucdp/about-ucdp|archive-date=2019-04-03|url-status=live}}</ref> The following subsections consider causes of war from system, societal, and individual levels of analysis. This kind of division was first proposed by [[Kenneth Waltz]] in ''[[Man, the State, and War]]'' and has been often used by political scientists since then.<ref name=Levy1998 />{{rp|143}}

====System-level====

There are several different [[international relations theory]] schools. Supporters of [[realism in international relations]] argue that the motivation of states is the quest for security, and conflicts can arise from the inability to distinguish defense from offense, which is called the [[security dilemma]].<ref name=Levy1998>{{cite journal|last1=Levy|first1=Jack S.|author-link1=:de:Jack Levy|title=The Causes of War and the Conditions of Peace|journal=Annual Review of Political Science|date=Jun 1998|volume=1|pages=139–65|doi=10.1146/annurev.polisci.1.1.139|doi-access=free}}</ref>{{rp|145}}

Within the realist school as represented by scholars such as [[Henry Kissinger]] and [[Hans Morgenthau]], and the [[neorealism (international relations)|neorealist]] school represented by scholars such as [[Kenneth Waltz]] and [[John Mearsheimer]], two main sub-theories are:
# [[Balance of power (international relations)|Balance of power]] theory: States have the goal of preventing a single state from becoming a hegemon, and war is the result of the would-be hegemon's persistent attempts at power acquisition. In this view, an international system with more equal distribution of power is more stable, and "movements toward unipolarity are destabilizing."<ref name=Levy1998 />{{rp|147}} However, evidence has shown power [[Polarity (international relations)|polarity]] is not actually a major factor in the occurrence of wars.<ref name=Levy1998 />{{rp|147–48}}
# [[Power transition theory]]: Hegemons impose stabilizing conditions on the world order, but they eventually decline, and war occurs when a declining hegemon is challenged by another rising power or aims to pre-emptively suppress them.<ref name=Levy1998 />{{rp|148}} On this view, unlike for balance-of-power theory, wars become ''more'' probable when power is more equally distributed. This "power preponderance" hypothesis has empirical support.<ref name=Levy1998 />{{rp|148}}
The two theories are not mutually exclusive and may be used to explain disparate events according to the circumstance.<ref name=Levy1998 />{{rp|148}} [[Liberalism (international relations)|Liberalism]] as it relates to international relations emphasizes factors such as trade, and its role in disincentivizing conflict which will damage economic relations. Critics respond that military force may sometimes be at least as effective as trade at achieving economic benefits, especially historically if not as much today.<ref name=Levy1998 />{{rp|149}} Furthermore, trade relations which result in a high level of dependency may escalate tensions and lead to conflict.<ref name=Levy1998 />{{rp|150}} Empirical data on the relationship of trade to peace are mixed, and moreover, some evidence suggests countries at war do not necessarily trade less with each other.<ref name=Levy1998 />{{rp|150}}

====Societal-level====
* [[Diversionary foreign policy|Diversionary theory]], also known as the "scapegoat hypothesis", suggests the politically powerful may use war to as a diversion or to rally domestic popular support.<ref name=Levy1998 />{{rp|152}} This is supported by literature showing out-group hostility [[Realistic conflict theory|enhances]] in-group [[Group cohesiveness|bonding]], and a significant domestic "rally effect" has been demonstrated when conflicts begin.<ref name=Levy1998 />{{rp|152–13}} However, studies examining the increased use of force as a function of need for internal political support are more mixed.<ref name=Levy1998 />{{rp|152–53}} U.S. war-time presidential popularity surveys taken during the presidencies of several recent U.S. leaders have supported diversionary theory.<ref name="MilitaryAdventurism">{{cite web| year = 2001| url = http://www.bepress.com/peps/vol7/iss3/3/| title = Peace Economics, Peace Science and Public Policy (p. 19)| access-date = 2010-02-07| url-status=dead| archive-url = https://web.archive.org/web/20110707224412/http://www.bepress.com/peps/vol7/iss3/3/| archive-date = 7 July 2011}} More recently studies (Lebow 2008, Lindemann 2010) demonstrated that striving for self-esteem (i.e. virile self images), and recognition as a Great Power or non-recognition (exclusion and punishment of great powers, denying traumatic historical events) is a principal cause of international conflict and war.
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====Individual-level====

These theories suggest differences in people's personalities, decision-making, emotions, belief systems, and biases are important in determining whether conflicts get out of hand.<ref name=Levy1998 />{{rp|157}} For instance, it has been proposed that conflict is modulated by [[bounded rationality]] and various [[cognitive biases]],<ref name=Levy1998 />{{rp|157}} such as [[prospect theory]].<ref name=Levy1997>{{cite journal|last1=Levy|first1=Jack S.|author-link1=:de:Jack Levy|title=Prospect Theory, Rational Choice, and International Relations|journal=International Studies Quarterly|date=Mar 1997|volume=41|issue=1|pages=87–112|url=http://www.ou.edu/uschina/texts/Levy.97.ISQ.ProspectTheory.pdf|doi=10.1111/0020-8833.00034|url-status=dead|archive-url=https://web.archive.org/web/20150924075824/http://www.ou.edu/uschina/texts/Levy.97.ISQ.ProspectTheory.pdf|archive-date=24 September 2015}}</ref>