Adolf Hitler came to power in Germany in 1933. He believed that the conditions imposed on Germany by the Allies after the First World War were unfair; he also wanted to conquer more land for the German people. He set about renegotiating treaties, building up arms, and testing Germany's military strength in nearby countries. The British government tried to avoid another war. However, when Hitler invaded Poland in 1939, Britain and France declared war in order to stop his aggression.