What was the main cause of World War II?

The main cause of World War II can be attributed to aggression by the Axis powers, particularly Germany and Japan. This aggression was characterized by expansionist policies and military invasions that aimed to acquire territory and resources. Germany, under Adolf Hitler, violated the Treaty of Versailles by reoccupying the Rhineland, annexing Austria, and then invading Poland in 1939, which directly triggered the war. Similarly, Japan sought to expand its influence in Asia, leading to invasions of China and later the attack on Pearl Harbor in 1941.

While economic instability, such as the Great Depression, played a role in creating conditions that facilitated the rise of totalitarian regimes, the decisive factor that ignited the conflict was the willingness of these aggressive states to pursue military expansion. Colonial disputes and the territorial aspirations of the Allies were not central to the outbreak of the conflict when compared to the actions taken by the Axis powers that directly challenged the sovereignty of other nations and violated international agreements.