World War II was the most devastating conflict in modern history, causing millions of casualties and leaving a lasting global impression. There are many causes that are argued to have led to this destructive war, but most historians agree that the main causes of World War II are the rise of Nazi Germany, the expanding military power of other countries, the Treaty of Versailles, and the weakening of international organizations such as the League of Nations.

The rise of Nazi Germany is the top cause of World War II which led to German expansionism and the formation of powerful military alliances in Europe to oppose them. Under the Nazis, Germany began a campaign of rearmament, which included buildups of their land and naval forces, as well as the development of new and more deadly weapons. This put growing pressure in other European countries to either join Nazi Germany or strengthen their weak defense forces.

The Treaty of Versailles is another main cause of the war. It imposed a harsh peace settlement on Germany and restricted the size of their armed forces. This led to increased tensions between the major powers in Europe and further weakened the League of Nations, which was unable to manage the escalating conflicts.

The military buildups of the different major powers are also among the major causes of World War II. As countries began to expand their military forces, there became a competition to have greater military power than their enemies. This created an arms race that resulted in an atmosphere of fear and aggression between nations.

In conclusion, World War II had several underlying causes, but the main causes of the war were the rise of Nazi Germany, the strengthening of the military power of other nations, the Treaty of Versailles, and the weakening of the League of Nations. These causes all worked together to create an environment of rivalry and conflict that laid the groundwork for World War II.