Chapter 20 : World War II Under Adolf Hitler, Nazi Germany invaded one country after another in the 1930s. At first Great Britain and France tried appeasement to avoid war, but when the Germans invaded Poland, Great Britain and France declared war on Germany. As the invasions continued, France surrendered, leaving Great Britain to fight Germany alone. Eventually Germany launched a large-scale invasion of the Soviet Union. Although the United States had remained neutral, it had supplied the British with war materials. To prevent the Americans from interfering with its expansion into East Asia and the Pacific, Japan attacked the United States fleet at Pearl Harbor, bringing America into the conflict. The war ended in Europe in May, 1945 with Germany's surrender to the Allies. Later that year the United States forced Japan's surrender when it dropped the atomic bomb on two Japanese cities.