Editing Preemptive war (section)

===League of Nations period (1919–1939)===
{{Main|Causes of World War II|Interwar period|Invasion of Poland}}
[[File:193109 mukden incident railway sabotage.jpg|thumb|Japanese experts inspect the scene of the "railway sabotage" at [[Mukden]] of the [[South Manchurian Railway]].]]
In the 1920s, the League peaceably settled numerous international disputes and was generally perceived as succeeding in its primary purpose. It was only in the 1930s that its effectiveness in preventing wars began to come into question. Such questions began to arise when it first became apparent in 1931 that it was incapable of halting aggression by [[Empire of Japan|Imperial Japan]] in [[Manchuria]]. In the [[Mukden Incident]], Japan claimed to be fighting a "defensive war" in [[Manchuria]], attempting to "preempt" supposedly-aggressive Chinese intentions towards the Japanese. According to the Japanese, the [[Republic of China (1912–1949)|Republic of China]] had started the war by blowing up a [[South Manchuria Railway|South Manchurian Railway]] line near [[Shenyang|Mukden]] and that since the Chinese were the aggressors, the Japanese were merely "defending themselves."' A predominance of evidence has since indicated that the railway had actually been blown up by Japanese operatives.<ref name="mukden incident">{{cite web|year=2010|url=http://ww2db.com/battle_spec.php?battle_id=18|title=Mukden Incident and Manchukuo: C. Peter Chen|access-date=2010-11-30}} Details of the Mukden Incident</ref>
[[File:Glivice radio tower.JPG|thumb|upright|[[Gliwice Radio Tower]] today. It was the scene of the [[Gleiwitz incident]] in September 1939]]
In 1933, the impotency of the League became more pronounced when notices were provided by Japan and [[Nazi Germany]] that they would be terminating their memberships in the League. [[Fascist Italy (1922–1943)|Fascist Italy]] shortly followed suit by exiting the League in 1937.<ref name="lon timeline">{{cite web|year=2006|url=http://www.indiana.edu/~league/timeline.htm|title=League of Nations Timeline|access-date=2010-11-30|archive-date=2016-08-27|archive-url=https://web.archive.org/web/20160827161853/http://www.indiana.edu/~league/timeline.htm|url-status=dead}} A timeline of all major League events.</ref> Soon, Italy and Germany also began engaging in militaristic campaigns designed to either enlarge their borders or to expand their sphere of military control, and the League was shown to be powerless to stop them.<ref name="lon timeline"/> The perceived impotency of the League was a contributing factor to the full outbreak of [[World War II]] in 1939.<ref name="lon impotence precipitates wwii">{{cite web|year=2010|url=http://www.factmonster.com/ce6/history/A0859217.html|title=Factmonster Encyclopedia— League of Nations: Successes and Failures|access-date=2010-11-30}} Description of the demise of the League of Nations.</ref> The start of World War II is generally dated from the event of [[Invasion of Poland|Germany's invasion of Poland]]. It is noteworthy that Germany claimed at the time that its invasion of [[Second Polish Republic|Poland]] was in fact a "defensive war," as it had allegedly been invaded by a group of Polish saboteurs, signaling a potentially-larger invasion of Germany by Poland that was soon to be under way. Thus, Germany was left with no option but to preemptive invade Poland to halt the alleged Polish plans to invade Germany. It was later discovered that Germany had fabricated the evidence for the alleged Polish saboteurs as a part of the [[Gleiwitz incident]].