Editing Operation Downfall (section)

{{short description|Allied plan to invade mainland Japan, WWII}}
{{Redirect|Invasion of Japan|the failed Mongol invasion attempts|Mongol invasions of Japan}}
{{Redirect|Soviet invasion of Japan|Soviet invasion of Manchuria which was under Japanese rule|Soviet invasion of Manchuria}}

{{Use American English|date=February 2021}}
{{Use mdy dates|date=October 2024}}
{{Infobox military operation
 |name          = Operation Downfall
 |partof        = the [[Pacific War]]
 |subtitle      = 
 |image         = Operation Downfall - Map.jpg
 |image_upright = 1.2
 |alt           = 
 |caption       = 
 |scope         = 
 |type          = 
 |location      = [[Mainland Japan]]
 |location2     = <!-- 2 through 10 for more locations -->
 |coordinates   = 
 |coordinates2  = <!-- 2 through 10 for more locations -->
 |map_type      = 
 |map_size      = 
 |map_caption   = 
 |map_label     = 
 |map_label2    = <!-- 2 through 10 for more locations -->
 |planned       = Before August 1945
 |planned_by    = {{ubl|[[Chester Nimitz]]|[[Douglas MacArthur]]|[[Joint Chiefs of Staff]]}}
 |commanded_by  = [[Douglas MacArthur]]
 |objective     = Defeat the [[Empire of Japan]]
 |target        = 
 |date          = <!-- {{start date|YYYY|MM|DD}} --> 
 |time          = 
 |time-begin    = 
 |time-end      = 
 |timezone      = 
 |executed_by   = See ''[[Operation Downfall order of battle|order of battle]]''
 |outcome       = Cancelled after the unconditional [[surrender of Japan]] on August 15, 1945 
 |casualties    = See ''[[#Estimated casualties|estimated casualties]]''
 |fatalities    = 
 |injuries      = 
|campaignbox=
{{Campaignbox Japan}}
{{Campaignbox Pacific War}}
}}

'''Operation Downfall''' was the proposed [[Allies of World War II|Allied]] plan for the invasion of the [[Japanese archipelago|Japanese home islands]] near the [[End of World War II in Asia|end of World War II]]. The planned operation was canceled when [[Surrender of Japan|Japan surrendered]] following the [[atomic bombings of Hiroshima and Nagasaki]], the [[Soviet–Japanese War|Soviet declaration of war]], and the [[Soviet invasion of Manchuria|invasion of Manchuria]].{{sfn|Giangreco|2009|p=xvi}} The operation had two parts: Operation Olympic and Operation Coronet. Set to begin in November 1945, Operation Olympic was intended to capture the southern third of the southernmost main Japanese island, [[Kyushu|Kyūshū]], with the [[Battle of Okinawa|recently captured]] island of [[Okinawa Island|Okinawa]] to be used as a staging area. In early 1946 would come Operation Coronet, the planned invasion of the [[Kantō Plain]], near [[Tokyo]], on the main Japanese island of [[Honshu]]. Airbases on Kyūshū captured in Operation Olympic would allow land-based air support for Operation Coronet. If Downfall had taken place, it would have been the largest [[amphibious operation]] in history, surpassing [[Normandy Landings|D-Day]].{{sfn|MacArthur}}

[[Geography of Japan|Japan's geography]] made this invasion plan obvious to the Japanese as well; they were able to accurately predict the Allied invasion plans and thus adjust their defensive plan, Operation Ketsugō [[w:ja:決号作戦|(ja)]], accordingly. The Japanese planned an all-out defense of Kyūshū, with little left in reserve for any subsequent defense operations. Casualty predictions varied but were extremely high, from the low hundreds of thousands to over a million on the Allied side and into the millions for the Japanese.{{sfn |Frank|p=340}}