World War II ended when the atomic bombing of Hiroshima and Nagasaki forced the Japanese government to surrender. Until then, however, Allied planners had operated on the assumption that they would have to invade and conquer Japan. Their plan for how to go about that was Operation Downfall.
Operation Downfall’s Stages
As drawn, Operation Downfall was to take place in two stages, Operation Olympic and Operation Coronet. First was Operation Olympic, scheduled for November, 1945. Its goal was to secure the southern third of Kyushu, the southernmost of Japan’s four main home islands. Olympic, was to commence with amphibious landings on three Kyushu beaches. The seized territory would provide airbases for land-based aircraft. It would also serve as the staging area for the second part of Operation Downfall, the even bigger Operation Coronet.
Planned for the spring of 1946, Coronet was directed at Honshu, the largest and most populous of Japan’s home islands. As it turned out, it was a good thing that Operation Downfall was never executed. After Japan surrendered, it was discovered that the Japanese had accurately predicted US intentions and the planned landing sites. Japanese geography was such that the only viable beaches for large amphibious landings were the ones selected by Allied planners for operations Olympic and Coronet.
Amphibious Invasions That Would Have Dwarfed D-Day
Even though the Japanese had accurately predicted the Allies’ planned invasion beaches, knowing what the Allies planned to do was not the same as being able to stop them from doing it. The planned landings would probably still have prevailed in the end through sheer brute force: the resources committed to the amphibious invasions of Japan dwarfed those of the D-Day landings in France. Operation Downfall was to draw on forty two aircraft carriers, twenty four battleships, and more than four hundred destroyers and destroyer escorts.
In addition to the US Navy’s carrier-borne airplanes, the US Army Air Forces was to provide tactical air support from the Fifth, Seventh, and Thirteenth Air Forces. As to the amphibious assaults, fourteen US Army and Marine divisions were committed to the initial landings. All of that was to be backed by a robust logistics chain, and ample supplies and munitions. Casualties however, as seen below, would likely have been horrific, their number depending on the degree of Japanese civilian resistance.
Operation Downfall Was Expected to Produce Horrific Casualties
In the war’s final months, disaster after disaster befell Japan. Its cities were bombed into ashes, its home islands were blockaded, and its population grew steadily hungrier, inching towards starvation. It was clear that Japan had lost the war. Rather than face that reality, Japan’s leaders immersed themselves in a toxic stew of suicidal defiance. To avoid the shame of surrender, they were determined not only to destroy themselves, but to commit national suicide and take Japan’s population with them. As the threat of invasion loomed ever larger, Japanese authorities were busy training even women and children to fight Allied soldiers with spears and pointy sticks. In light of that fanaticism, planners contemplated worst case scenarios of more than a million Allied casualties, and tens of millions Japanese.
Operation Downfall’s planners went about their preparations in the dark about the highly secretive Manhattan Project. Even when an atomic bomb was successfully tested in July, 1945, the people drawing up plans for an invasion of Japan did not fully grasp the new weapon’s potential. They pictured the new nuclear weapons as “really big bombs”, and had some nebulous ideas about incorporating them into the invasion by using them to support Operation Olympic’s amphibious landings that November. However, the atomic bombs were dropped instead on Hiroshima and Nagasaki in August, 1945. The twin blows finally shocked the Japanese government into seeing reason, ended the war, and eliminated the need for Operation Downfall.
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Some Sources & Further Reading
History Halls – Why Did Many Japanese Soldiers Refuse to Surrender After World War II Ended?
Skates, John Ray – The Invasion of Japan: Alternative to the Bomb (1994)
US Army War College Quarterly (Autumn 1994) – Downfall: The Invasion That Never Was
