World War 2 was caused by several interrelated factors in the late 1930s including German resentment over the Treaty of Versailles, the worldwide Great Depression, the rise of nationalist and fascist leaders like Hitler in Germany and Mussolini in Italy, and the policy of appeasement pursued by Britain and France. By 1939 Germany and Italy had formed an alliance called the Axis Powers and had occupied much of Europe. In Asia, Japan had also become increasingly militaristic and expansionist, occupying Manchuria in 1931 and much of China by 1937. These events led the world into the largest and deadliest war in history.