thumb|right|320px|Devastation in Tokyo following US Army Air Force firebombing in March 1945
Operation Downfall was the proposed Allied plan for the invasion of the Japanese home islands near the end of World War II.
The operation had two parts, Operation Olympic, intended to capture the southern third of the southernmost main Japanese island, Kyūshū, and Operation Coronet, the planned invasion of the Kantō Plain, near Tokyo, on the main Japanese island of Honshu. Olympic was scheduled for November 1945, to be followed by Coronet in early 1946.
If Downfall had taken place, it would have been the largest amphibious operation in history, surpassing D-Day. The planned operation was canceled when Japan surrendered following the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, and the invasion of Manchuria.
Order of Battle for Olympic
Allied
<big>Supreme Commander, Allied Forces Pacific</big><br>
<big>General Douglas MacArthur</big>
Ground forces
Should these four corps prove insufficient to accomplish the tasks assigned, elements earmarked for Coronet would be used to reinforce Sixth Army at the rate of three divisions per month beginning about 30 days after the initial landings.
: 22px <big>U.S. Sixth Army</big>
: General <big>Walter Krueger</big>
:: Peripheral landings
::: 22px 40th Infantry Division (Landing on Yakushima and Koshikijima Islands)
::: 14px 158th Infantry Regiment (Landing on Tanegashima)
:: 22px I Corps (Landing at Miyazaki)
:::: 145th Division
:::: 312th Division
:::: 351st Division
:::: 124th Independent Mixed Brigade
:::: 57th Division (20,000 men)
:::: 4th Tank Brigade
::: Southeastern Kyūshū — 57th Army
::: Lieut. General Nishihara Kanji (150,000 men)
:::: Tanegashima—109th Independent Mixed Brigade (5,900 men)
:::: Miyazaki—154th Division, 156th Division, 212th Division