Operation Downfall: The Planned Allied Invasion of Japan
By mid-1945, Japan was defeated but unwilling to surrender. The US planned Operation Downfall, a two-phase invasion of the Japanese home islands. Phase one, Operation Olympic, targeted Kyushu on November 1, 1945 (X-Day), involving 582,000 troops initially, with reinforcements bringing total to 767,000. Expected casualties were 268,000 based on Okinawa's 35% rate. Phase two, Operation Coronet, aimed at Honshu near Tokyo on March 1, 1946 (Y-Day), with 1,171,646 US troops plus Allied reinforcements. Japan's defense plan, Operation Ketsugo, amassed over 900,000 troops in Kyushu, plus kamikaze attacks, suicide boats, and a civilian militia of 2.4 million under the slogan "the glorious death of the 100 million." The invasion was never executed; Japan surrendered after the atomic bombings and Soviet invasion of Manchuria. An Allied victory was considered inevitable due to US superiority in population, industry, and resources.
Key facts
- Operation Downfall was the planned Allied invasion of Japan, divided into Operation Olympic (Kyushu) and Operation Coronet (Honshu).
- Operation Olympic was scheduled for November 1, 1945 (X-Day) with 582,000 initial troops, later reinforced to 767,000.
- Operation Coronet was scheduled for March 1, 1946 (Y-Day) with 1,171,646 US troops plus Allied reinforcements.
- Japan's defense plan, Operation Ketsugo, involved over 900,000 troops in Kyushu, kamikaze attacks, suicide boats, and civilian militia.
- Expected US casualties for Olympic were 268,000 based on Okinawa's 35% casualty rate.
- Japan planned to mobilize 2.4 million civilians in Kyushu under the slogan 'the glorious death of the 100 million'.
- The invasion was never carried out; Japan surrendered after atomic bombings and Soviet invasion of Manchuria.
- An Allied victory was considered inevitable due to US superiority in population, industry, and resources.
Entities
Institutions
- United States
- Empire of Japan
- Imperial Japanese Navy
- Imperial Japanese Army
- Allies
- US Marine Corps
- US Army
- Soviet Union
- National WWII Museum
- US Army Center of Military History
- Naval History and Heritage Command
- Polish National Archives
Locations
- Japan
- China
- Pacific
- Pearl Harbor
- Guam
- Wake Island
- Philippines
- Hong Kong
- Malaya
- Burma
- Okinawa
- Kyushu
- Honshu
- Tokyo
- Kanto Plain
- Europe
- Manchuria
- New Orleans
- United States