Series: Operation Downfall

As 1944 turned into 1945 an Allied victory in the Pacific was creeping closer to reality. Little by little American forces were rolling up the Japanese defenses one island at a time as they pushed the invaders back further and further towards the Japanese mainland. Guam had been taken, the Philippines were being contained and bombing on Iwo Jima was underway. In this atmosphere of cautious optimism the ideas for Operation Downfall, as it would be called, were being hashed out by the Combined Chiefs of Staff at the Argonaut Conference ¹The codename for The Yalta Conference, the 1945 wartime meeting between Franklin D. Roosevelt, Winston Churchill, and Joseph Stalin held on the tiny island of Malta in the Mediterranean. The conference called for the defeat of Japan within eighteen months of the surrender of Germany, and this would entail a possible amphibious landing on the Japanese mainland itself. At the time the Manhattan Project was a closely guarded secret so the members at the conference didn’t even take its existence into account.

The conference had many other factors to think about also. How could they force an unconditional Japanese surrender with the least amount of Allied casualties in the shortest period of time? Originally a joint British-American team had written a document entitled “Appreciation and Plan for the Defeat of Japan” where they didn’t foresee an invasion until after 1947 but the conference felt that dragging the war out that far would have dangerous consequences to American morale at home. And not only would the Allies face Japanese military units but also a “fanatically hostile population”. Fighting the Japanese military was one thing, facing an entire population armed with various weapons carrying out banzai attacks was another. The death toll on both sides could have been tremendous.

In light of this the US Navy urged a sea blockade and airpower to bring about surrender. The US Army Air Force, using captured airbases in China and Korea would be able to bombard Japan into submission.²A sea blockade had helped the US defeat another enemy roughly 80 years previous to this – The Confederate States of America. The US Army, though, believed that the strategy could prolong the war for an indeterminate amount of time and needlessly waste lives. In light of this the Army’s opinion won out.

And so planning on the two-part invasion began. It was to be broken into two operations, Olympic and Coronet with Olympic scheduled to begin on X-Day – November 1, 1945.³Info for this post came from both Military History Encyclopedia on the Web and Wikipedia.

We’ll talk about the first phase, Olympic, next time.

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Downfall would have been the largest amphibious landing in history, including 42 aircraft carriers, 24 battleships, 400 destroyers and other ships. Fourteen U.S. divisions A division is a large military unit usually consisting of around ten to twenty thousand soldiers. would take part also as they used Okinawa as a staging base and then seized the southern portion of the island of Kyushu. The invasion was scheduled to start on November 1, 1945. But there were some other considerations that the planners had to take into account.

There was, naturally, to be a deception plan leading up to the Olympic invasion. By having such a plan it was hoped, as all deception plans in war were, that Allied casualties would be minimized because the enemy force would believe that it needed to focus itself elsewhere. The plan to precede Olympic was Operation Pastel, wherein which the Joint Chiefs of Staff would attempt to fool the Japanese into thinking that a direct invasion of the southern islands had been rejected and instead that the Allies would focus first on Japanese forces still in mainland China. The first strike would be a false Allied attack on China’s Chusan-Shanghai area, with a fictional landing date of October 1, 1945. This was to be followed by one of the smaller southern Japanese islands, Shikoku. After this the Allies hoped to surprise the Japanese with the Olympic invasion.

All of this was leading up to X-Day, as it was called, where the Alllied forces would invade Kyushu along the eastern, southeastern, southern and western coasts of the island near the towns of Miyazaki, Ariake, and Kushikino. The invasion force was to consist of three main groups landing on 35 different beaches, all codenamed after makes of automobiles. The Eastern Assault Force consisting of the 25th, 33rd and the 41st Infantry Divisions, would land near Miyaski and quickly move inland to capture Miyazaki and its nearby airfield. The Southern Force which was to consist of the 1st cavalry Division, the 43rd Division and American Division would land inside Ariake Bay and capture Shibushi and to capture, further inland, the city of Kanoya and its surrounding airfield. On the western shore of Kyushu near Kushikino the 2nd, 3rd, and 5th Marine Divisions would land and split, part of which would head inland to capture Sendai while the other half captured the port city of Kagoshima. Once these areas were secured more Allied reinforcements consisting of three American divisions would be brought in each month to strengthen the hold on the occupied portion of Kyushu.

Before and during all of this activity the U.S. Twentieth Air Force would be bombing strategic targets such as railroads, airfields and the various beaches that were to be hit. With a successful bombing campaign it was hoped that they could minimize any fast means that reinforcements could utilize to arrive at the various invasion points.

The four month timetable for Olympic was not to conquer the entire island but to gain a foothold for the Allies to jump off of and use as a staging ground for the even bigger invasion – Coronet. More on it in part 3.¹The info for this piece came, once again, from Wikipedia, the the Combined Arms Research Library

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