invasion of Japan

invasion of Japan
Conflict	Invasion of Japan
Partof	the Pacific War during World War II
Date	Projected for late 1945 – 1946
Place	Home Islands of Empire of Japan
Result	Cancelled following the surrender of Japan
Combatant1	Allies
Combatant2	Empire of Japan
Commander1	Douglas MacArthur, Chester W. Nimitz, Curtis LeMay
Commander2	Hirohito, Kantarō Suzuki, Yoshijirō Umezu

invasion of Japan was the proposed Allied military operation to end World War II by invading the Japanese archipelago. Codenamed Operation Downfall, it was planned as a two-phase assault involving the largest amphibious landing in history. The operation was rendered unnecessary by the surrender of Japan following the atomic bombings of Hiroshima and Nagasaki and the Soviet invasion of Manchuria.

Background and planning

Following decisive Allied victories at the Battle of Iwo Jima and the Battle of Okinawa, the Imperial Japanese Army refused to capitulate. The Potsdam Declaration in July 1945 demanded unconditional surrender, which the Supreme War Council publicly rejected. Allied planners, including the U.S. Joint Chiefs of Staff, concluded that a full-scale invasion of the Home Islands was necessary to defeat Japan. The overall strategy, Operation Downfall, was developed under the direction of Douglas MacArthur and Chester W. Nimitz, with detailed planning coordinated by the Joint Chiefs of Staff.

Allied preparations

Allied preparations involved massive redeployments from the European Theater. The First United States Army and the Eighth United States Army were designated for the initial assault, with the British Pacific Fleet and Royal Australian Air Force providing support. The Twentieth Air Force, commanded by Curtis LeMay, continued its strategic bombing campaign from bases in the Mariana Islands. Enormous stockpiles of munitions and landing craft were assembled across the Pacific Ocean, with staging areas established in the Philippines and on Okinawa Island.

Japanese defenses

Japanese defenses were organized under the broad strategy of Operation Ketsugō. The Imperial Japanese Army mobilized millions of civilian militiamen under the Volunteer Fighting Corps and planned to deploy thousands of kamikaze aircraft from the Imperial Japanese Navy Air Service. Defensive fortifications were concentrated on the southern island of Kyushu, predicted to be the first Allied target. Senior commanders like Yoshijirō Umezu and Hajime Sugiyama intended to inflict catastrophic casualties on invading forces, relying on entrenched positions and fanatical last stands.

Projected operations

Operation Downfall consisted of two major phases. The first, Operation Olympic, was scheduled for November 1945 and aimed to secure southern Kyushu using the Sixth United States Army. The second phase, Operation Coronet, planned for March 1946, was a direct assault on the Kantō Plain near Tokyo by the combined First United States Army and Eighth United States Army, potentially including a Commonwealth corps with troops from the British Army and Canadian Army. These operations would have been preceded by an extensive naval bombardment from the United States Third Fleet.

Estimated casualties and consequences

Casualty estimates varied widely but were universally projected to be extremely high. The United States Department of War produced studies, including those by the Joint War Plans Committee, forecasting hundreds of thousands of Allied casualties and millions of Japanese military and civilian deaths. Planners anticipated fierce resistance akin to the Battle of Saipan and the Battle of Okinawa on a national scale. The potential use of chemical weapons by both sides and widespread famine due to the Allied naval blockade were considered likely catastrophic consequences for the Japanese population.

Cancellation and aftermath

The invasion was cancelled following the atomic bombings of Hiroshima and Nagasaki by the Enola Gay and Bockscar, coupled with the Soviet invasion of Manchuria. Emperor Hirohito announced Japan's acceptance of the Potsdam Declaration in his Jewel Voice Broadcast. The formal Japanese Instrument of Surrender was signed aboard the USS Missouri (BB-63) in Tokyo Bay, commencing the Occupation of Japan under the Supreme Commander for the Allied Powers. The avoided invasion profoundly shaped post-war United States–Japan relations and fueled decades of historical debate regarding the necessity and morality of the atomic bombings of Hiroshima and Nagasaki.

Category:World War II Category:Military history of Japan Category:Proposed military operations