In a matter of months, however, Hitler broke the pledge and annexed the rest of Czechoslovakia. Despite this, the British and French chose to do nothing, wanting to avoid war at any cost. Hitler then formed a secret non-aggression pact with the Soviet Union, despite the fact that the Soviet Union was Communist and Germany was Nazi. Also in the 1930s, Italy conquered Ethiopia. The Soviets too began annexing neighboring countries. Japan began taking aggressive actions towards China. After Japan opened itself to trade with the West in the mid-19th century, its leaders learned to take advantage of Western technology and industrialized their country by the end of the century. By the 1930s, Japan's government was under the control of militarists who wanted to establish an empire in the Asia-Pacific region. In 1937, Japan invaded China. In 1939, German forces invaded Poland, and soon the country was divided between the Soviet Union and Germany. France and Britain declared war on Germany, World War II had begun. The war featured the use of new technologies and improvements on existing ones. Airplanes called bombers were capable of travelling great distances and dropping bombs on targets. Submarine, tank and battleship technology also improved. Most soldiers were equipped with hand-held machine guns and armies were more mobile than ever before. Also, the British invention of radar would revolutionize tactics. German forces invaded and conquered the Low Countries and by June had even conquered France. In 1940 Germany, Italy and Japan formed an alliance and became known as the Axis Powers. Germany next turned its attention to Britain. Hitler attempted to defeat the British using only air power. In the Battle of Britain, German bombers destroyed much of the British air force and many British cities. Led by their prime minister, the defiant Winston Churchill, the British refused to give up and launched air attacks on Germany. Eventually, Hitler turned his attention from Britain to the Soviet Union. In June 1941, German forces invaded the Soviet Union and soon reached deep into Russia, surrounding Moscow, Leningrad, and Stalingrad. Hitler's invasion came as a total surprise to Stalin; however, Hitler had always believed sooner or later Soviet Communism and what he believed were the "inferior" Slavic peoples had to be wiped out. The United States attempted to remain neutral early in the war. However, a growing number feared the consequences of a Fascist victory. President Roosevelt