There were different causes of World War II but three causes were main and these three main causes were; Treaty of Versailles, Rise of Hitler and Japanese territorial expansion.
Treaty of Versailles was also known as the seed of the World War II, Under this treaty, Germany was declared guilty by the Allied countries and they imposed humiliating sanctions on Germany.
The rise of Hitler and his Nazi Party was another cause of World War II which through the whole of Germany into the mouth of War.
Japanese territorial expansion led to the attack on pearl harbor which was become another cause of the II world war.
Among the causes of World War II were, to a greater extent, the political takeover in 1933 of Germany by Adolf Hitler and his Nazi Party and its aggressive foreign policy, and to a lesser extent, Italian Fascism in the 1920s, and Japanese militarism preceding an invasion of China in the 1930s.(wiki.com)
