In the 1930s the rise of fascism and communism in Europe and the expansion of the German and Italian empire and also the expansion of Japanese empire in Asia saw the United States move from a policy of isolationism to supporting traditional allies and defending democracy. The United States became directly involved in World War 2 after the Japanese attack on Pearl Harbour.
The rise of fascism in Europe began when Germany turned to Adolf Hitler, an extremist. The Fascists, under Benito Mussolini, became powerful in the 1930s. Mussolini was able to make the country come together and wanted to gain back the territory that Germany had lost from the Treaty of Versailles. Communism had started to rise when Joseph Stalin took over the Soviet Communist Party. In July 1939, the Soviet Union, under the leadership of Stalin, signed a Non-Aggression Pact with Germany. Germany no longer had the fear of having to fight a war on two fronts.
Both communism and fascism were seen as potential threats to democracy. Germany, Italy joined in an alliance with Japan. By 1941, they had expanded their empire. Germany had invaded Poland. Italy launched an invasion of Egypt, Sudan and North Africa. In the Pacific, Japan was becoming successful and extended its empire into China and French Indo-China. Not only were they threats to democracy and balance of world power but to economic interests of Britain, USA, France and Holland. By 1941 Britain were under threat.
The United States involvement in World War 2 was not inevitable as initially the U.S adopted a policy of isolationism. When Franklin Roosevelt became president, he pledged that the United States would become 'the good neighbour' in world affairs. This meant that 'no state has the right to intervene in the internal or external affairs or...