World War II began September 1, 1939 in Europe. The United States entered the war one day after December 7, 1941, when Axis Power Japan attacked the U. S. Naval Base at Hawaii. On June 6, 1944, American forces joined by other Allied forces invaded German-controlled France. Germany surrendered May 8, 1945, and the war in Europe came to an end. The U. S. dropped the first atomic bomb on Hiroshima on August 6, 1945. The war with Japan continued until Japan surrendered August 14, 1945. (Because of time zone date variations, the date of surrender was August 14 (in the US) or 15 (in Japan). The surrender papers were signed on September 2, 1945, in Japan on the USS Missouri. World War II was officially over. While estimates vary, 70 million people were killed during the war (about 3% of the world’s population); 24 million of whom were military casualties. The United States suffered 418,000 military and civilian deaths.
Documents recovered from the Japanese military at the end of WWII indicated extensive preparations and plans to defend the island from invasion and occupation by the Allies. The Japanese strategy was to inflict such high casualties on US forces that the US would simply seek an end to the conflict without occupying Japan. Japan would dedicate 900,000 soldiers to defend the probable invasion point. The 19 remaining Japanese destroyers would plan suicide missions to sink US naval troop carriers inflicting high casualties. 3,330 suicide boats and 4,000 Japanese frogmen would engage in suicide missions to sink US landing craft during the invasion, again inflicting very high casualties. Japan would hold back their extensive (12,700 planes) air force until the invasion had begun and commit them in kamikaze attack waves of 300 to 400 planes each hour until all their planes were gone. All Japanese citizens were mobilized to fight to the death beside the military. Lastly, at the beginning of the invasion, Japan would murder the 15,000 allied prisoners it held.
The US invasion of Japan plan was code named Downfall. The US would commit 1.7 million troops. The invasion was controversial, with generals and admirals advocating for and against an invasion. In July 1945, US War Department estimates put US casualties at between 1.7 million to 4 million including 400,000 to 800,000 deaths. The War Department estimated that 5 to 10 million Japanese would be killed in an invasion.
