What was the main cause of World War II?

The main cause of World War II was the aggressive expansionism by Axis Powers, particularly Germany, Italy, and Japan. This expansionist agenda was driven by a desire for territorial gain and the belief in national superiority, often framed in the context of historical grievances or a need to secure resources. For instance, Germany, led by Adolf Hitler, sought to overturn the Treaty of Versailles, expand German territory to create Lebensraum (living space) for its population, and establish dominance in Europe. Similarly, Japan aimed to expand its empire in Asia, seeking resources to support its industrial economy and confronting Western powers.

This aggressive behavior directly violated international treaties and norms, leading to increasing tensions and conflicts. Events such as the invasion of Poland by Germany in 1939 acted as the immediate catalyst for the war, demonstrating how this expansionism was central to the outbreak of fighting. While economic factors and the rise of communism influenced the global landscape, it was the decisive and proactive military actions of the Axis Powers that ultimately triggered World War II. Disputes over colonial territories, while relevant in the wider context of 20th-century conflicts, did not hold the same immediate significance in igniting this particular war.