4. The Horrific Costs of an Invasion of Japan
Japanese geography meant that the only viable beaches for large amphibious landings were the ones selected by the planners of operations Olympic and Coronet. The Allies would still have prevailed in the end: the resources committed to the operation dwarfed those of the D-Day landings in France. They included 42 aircraft carriers, 24 battleships, 400 destroyers and destroyer escorts, tactical air support from the Fifth, Seventh, and Thirteenth Air Forces, and 14 divisions for the initial landing. Casualties, however, would likely have been horrific.
Worst case scenarios envisioned over a million Allied and tens of millions of Japanese casualties. Such high estimates are lent support by the fact that Japanese authorities were busy training even women and children to fight the invaders with spears and pointy sticks. At the time, Olympic’s planners were unaware of the highly secretive Manhattan Project. When the US successfully tested an atomic bomb in July 1945, nuclear weapons’ potential was not fully understood by planners. Envisioned simply as “really big bombs”, they had nebulous ideas of using nukes in the November invasion to support the amphibious landings.