The Axis, which was forged in 1936, included an alliance of three nations: Germany, Italy, and Japan. These major powers were joined by six smaller countries, the Axis satellites: Albania, Bulgaria, Finland, Hungary, Romania, and Thailand. But together these countries never comprised the unified front and strength that the Allied powers did.

Germany started the war on September 1, 1939, and was joined in June 1940 by Italy and Albania. In the middle of 1941 Bulgaria, Hungary, Romania, and Finland joined the Axis effort. Japan, which was already fighting with China (in the Sino-Japanese War), entered the fray on December 7, 1941, with its attack on the U.S. naval base at Pearl Harbor, Hawaii. Thailand was the last Axis country to enter the war, on January 25, 1942.