How MacArthur Was Going to Invade Japan

In 1966, two years after the death of Gen. Douglas MacArthur, the U.S. Army published the Reports of General MacArthur. Compiled by MacArthur’s staff, headed by Maj. Gen. Charles Willoughby and with the assistance of Prof. Gordon W. Prange, who was on leave from the University of Maryland, the Reports detailed the operations of forces under MacArthur’s command in the southwest Pacific, and included a chapter on “Operation Downfall,” the planned invasion of Japan.

In announcing their publication, Gen. Harold K. Johnson, then Chief of Staff of the U.S. Army, described them as “an illuminating record of momentous events influenced in large measure by a distinguished American soldier.”

The planning for Operation Downfall began in early 1945 at the Argonaut Conference in Malta, where the Combined Chiefs of Staff with the approval of President Roosevelt and Prime Minister Churchill set forth the following objectives for the Pacific War:

Following the Okinawa operation, to seize additional positions to intensify the blockade air bombardment of Japan in order to create a situation favorable to: An assault on Kyushu for the purpose of further reducing Japanese capabilities by containing and destroying major enemy forces and further intensifying the blockade and air bombardment in order to establish a tactical condition favorable to the decisive invasion of the industrial heart of Japan through the Tokyo Plain.

In March 1945, the U.S. Joint Chiefs of Staff, assuming that Germany would be defeated by early July 1945, divided Downfall into two main operations: Olympic, the assault on Kyushu scheduled for Dec. 1, 1945; and Coronet, the invasion of Honshu scheduled for March 1, 1946.  On April 3, 1945, the Joint Chiefs instructed MacArthur, in coordination with Adm. Chester Nimitz and Gen. Hap Arnold, to begin planning for the invasion of Japan.

MacArthur suggested to General George Marshall three approaches to bringing about the surrender of Japan:

First, the Allies could encircle Japan by further ... expansion to the westward, at the same time deploying maximum air power preparatory to attacks on either Kyushu or Honshu in succession, or on Honshu only. A second course would be to isolate Japan completely by seizing bases to the west and endeavoring to bomb her into submission without actually landing in force on the Homeland beaches. The third course open was to attack Kyushu directly and install air forces to cover a decisive assault against the principal island of Honshu.

MacArthur explained the advantages and disadvantages of all three strategies, and concluded that the third option would be the most effective in terms of attaining the objective timely and at reasonable cost. “[I]t ... would,” said MacArthur, “permit application of full power of our combined resources, ground, naval, and air, on the decisive objective.” Nimitz, according to the Reports, suggested several modifications but in general agreed with MacArthur’s plan, and both MacArthur and Nimitz advised Marshall to advance the date of the invasion of Kyushu to Nov. 1, 1945. After V-E Day in May 1945, the Joint Chiefs issued the directive for Olympic, giving MacArthur principal command of the invasion forces and setting Nov. 1 as the date for the assault on Kyushu.

The plans for Downfall assumed that Japan would vigorously defend its main islands with both military forces and “a fierce and active resistance by the entire population.” It was further anticipated that “massed Kamikaze attacks” would be launched against the invading American forces.

The Reports noted that the Japanese High Command in April 1945 issued its planned defense of the main islands, designated “Ketsu Operation.” The Homeland defenses consisted of “30 line-combat divisions, 24 coastal-combat divisions, and 23 independent mixed brigades, 2 armored divisions, 7 tank brigades, and 3 infantry brigades.” In addition, 8,000 “suicide or special- attack planes” and special attack boats and midget submarines were produced.

The planned U.S. invasion of Kyushu would be preceded by “one of the heaviest neutralization bombardments by naval and air forces ever carried out in the Pacific.” B-29 bombers would pound Kyushu from the air, while carrier task forces conducted coastal raids to attack Japan’s air and naval forces and to disrupt enemy communications. The last 10 days leading up to the landing “would see the massed bombing power of all available planes, both land and carrier-based, directed in a mighty assault to reduce the enemy’s defenses ...” The staging areas for the assault would be Hawaii, the Marianas, the Philippines, and the Ryukus. It was hoped that, as in the D-Day landings in Normandy, deception operations would be able to confuse Japan’s military and political leaders as to the precise locations of the assaults.