1. His desire to expand German territory and create a "Greater Germany". Hitler believed that Germany had been cheated out of territory in the Treaty of Versailles, which ended World War I, and he wanted to reclaim this land. He also believed that Germany needed more Lebensraum ("living space") for its growing population.
2. His hatred of Jews and other minority groups. Hitler was virulently anti-Semitic, and he saw the Jewish people as a threat to Germany. He also hated other minority groups, such as the Roma (Gypsies) and the Slavs.
3. His alliance with Japan and Italy. In 1936, Germany signed the Anti-Comintern Pact with Japan and Italy, which was a mutual defense treaty against the Soviet Union. This alliance gave Hitler the confidence to start the war, as he knew that he would have support from two other powerful countries.
4. The failure of the League of Nations. The League of Nations was an international organization that was created after World War I to promote peace and security. However, the League was unable to stop Hitler from starting the war, as it lacked the military power to enforce its resolutions.
5. The appeasement policy of the Western powers. The Western powers, including Great Britain, France, and the United States, pursued a policy of appeasement towards Hitler in the years leading up to the war. This meant that they made concessions to Hitler in the hopes of avoiding war. However, this policy only emboldened Hitler and made him more likely to start the war.
In conclusion, there were many factors that contributed to Hitler's decision to start World War II. These factors included his desire for territorial expansion, his hatred of Jews and other minority groups, his alliance with Japan and Italy, the failure of the League of Nations, and the appeasement policy of the Western powers.