By restricting the sale of strategic materials to hinder Japan's aggression in the Pacific, they tried to stop Japan from building an army to enter the Second World War. However, Japan knew that the United States had neglected their own defences. They were trying to stay out of the war and believed that they would not be attacked by any other nation. One of Roosevelt's election promises was that no American boy would have to go to war. The USA had to change that belief once Pearl Harbour was bombed.