World War II: Operation Olympic, X-Day Invasion of Japan & A-Bomb Decision Documents

World War II: Operation Olympic, X-Day Invasion of Japan & A-Bomb Decision Documents

1,589 pages of documents and historical studies concerning Operation Olympic, the planned invasion of Japan and the decision to use the atomic bomb against Japan.

Operation Olympic was a part of Operation Downfall along with Operation Coronet. Operation Downfall was the proposed Allied plan for the invasion of the Japanese home islands.

The planned operation was canceled when Japan surrendered in the days following the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war against Japan and the invasion of Manchuria. Set to begin in November 1945, Operation Olympic was intended to capture the southern third of the southernmost main Japanese island, Kyūshū, with the recently captured island of 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.

Casualties were expected to be very heavy and it was hoped that the use of atomic bombs might shock the Japanese into surrendering. The first bomb was dropped on Hiroshima on 6 August 1945. On 8 August the Soviet Union declared war on Japan and launched a massive attack in Manchuria. The Soviet blow had great diplomatic and political impact. On 9 August a second atomic bomb was dropped on the city of Nagasaki. On 15 August 1945 the Japanese surrendered.

Documents Include:

Einstein, Roosevelt, Sachs and Bush Correspondence

Albert Einstein, Franklin Roosevelt, Roosevelt advisor Alexander Sachs and Manhattan Project Director Vannevar Bush correspondences related to the creation of the Manhattan Project. In August 1939, Albert Einstein sent a letter to President Franklin Roosevelt warning of the possibility that Nazi Germany could build a new weapon which was more powerful and more destructive than any weapon ever known to mankind.

Includes the “Einstein–Szilárd letter” which was a letter written by Leó Szilárd and signed by Albert Einstein that was sent to the United States President Franklin D. Roosevelt on August 2, 1939. Written by Szilárd in consultation with fellow Hungarian physicists Edward Teller and Eugene Wigner, the letter warned that Germany might develop atomic bombs and suggested that the United States should start its own nuclear program. It prompted action by Roosevelt, which eventually resulted in the Manhattan Project developing the first atomic bombs

 
Military Intelligence Files

118 selected pages of U.S. military files covering the final months of the war with Japan. Documents cover U.S. invasion of Japan planning and the A-Bomb decision.

Files show the MacArthur/Nimitz rivalry over command control and military planners' sensitivity about confronting President Truman over casualty estimates, a total estimate of roughly "a quarter of a million."

Documents include coverage of anticipated Japanese reaction to an invasion of southern Kyushu, details of the planned campaign against Japan (codenamed Operation Olympic), cables to Potsdam regarding the A-Bomb test of 16 July, and instruction to General Carl Spaatz on use of the atomic bomb against a Japanese target.

 
Harry S. Truman Presidential Papers - Atomic Bomb Decision

600 pages of files dating from 1945 to 1953. Documents include coverage of the Groves Project AKA the Manhattan Project, minutes of the meeting held at the White House on Monday, 18 June 1945, evaluation of situation regarding the War in the Pacific against the Japanese, strategic bombing survey, study of war-time use of the atomic bomb by the Interim Committee chaired by Robert Oppenheimer, Truman diary entries, and Truman's reaction to the historical response to his decision to drop the bomb.

 
Logistical Plan for Operations Against Kyushu (1944)

By the Joint Logistics Committee.

Abstract: The enclosed report by the Joint Logistics Plans Committee is circulated for consideration by the Joint Logistics Committee. Since publication of J.W.P.C. 235/ 3, certain modifications in concept have been made and considered in the formulation of the attached plan. In view of the differing bases upon which these two plans were formulated, the Joint War Plans Committee and the Joint Logistics Plans Committee have informally agreed to review and combine both papers. Logistical plan for support of operations against Kyushu: Index: Enclosure-Report, Appendix-Logistical Plan for Support of Operations against Kyushu , Annex "A" Orientation Map, Annex "B" Tactical map, Annex "C" General map showing terrain and transportation, Annex "D" Units and personnel, Annex "E" Construction Requirements with Tab "A" Construction requirements summary of construction personnel, equipment and material required, Tab "B" Detail of construction projects required.

 
"Downfall" Strategic Plan, G-2 Estimate of the Enemy Situation (03-24-1945)

G-2 estimate of the Japanese situation with respect to operations against Kyushu and Honshu by theGeneral Headquarters, U.S. Army Forces in the Pacific. 

Contents include the summary of the enemy situation trends, command structure, ground forces, air forces, naval forces, merchant shipping position, terrain (Kyushu and Tokyo Plain of Honshu), and enclosures.

 
"DOWNFALL" Strategic Plan for Operations in the Japanese Archipelago May 28, 1945

Abstract:

1. The attached Strategic Plan constitutes the basis for directives for operations to force the unconditional surrender of JAPAN by seizure of vital objectives in the Japanese Archipelago.

2. Pending the issue of directives based thereon, the Plan is circulated to senior Commanders and Staff Sections of United States Army Forces in the Pacific and to the Commander- in-Chief, United States Pacific Fleet, as a general guide covering the larger phases of allocation of means and of coordination in order to facilitate planning and implementation, both operational and logistic. It is not designed to restrict executing agencies in detailed development of their final plans of operations.

3. The Plan is being forwarded to the Commanding General, Twentieth Air Force for his information and guidance.

4. Directives and Staff Studies covering the several operations to be conducted will be issued by Headquarters concerned at appropriate times.

 
Staff Study Olympic Operations in Southern Kyushu  (May 28, 1945)

This Staff Study is derived from "DOWNFALL",  Strategic Plan for , Operations in the Japanese Archipelago, General Headquarters, United States Army Forces in the Pacific, 20 May 1945. It covers the operations of United States Army and Navy Forces in the Pacific to occupy Southern Kyushu with target date ("X" Day) of 1 November 1945.

 
G-2 Estimate of the Enemy Situation, Olympic Operation,  (August 1, 1945)

G-2 estimate of the Japanese situation with respect to Olympic Operation (Southern Kyushu) by Assistant Chief of Staff, G-2, Headquarters Sixth Army

Abstract: G-2 estimate of the enemy situation with respect to Olympic Operation (Southern Kyushu). By midsummer of 1945 there was little that Japan could look backward to with pride or forward to with hope. The crescendo of Allied advance had grown apace, and with portentous results. The sequel to Okinawa could only be an attack upon some part of the Inner Zone and presumably would be an invasion of the homeland. Japan acknowledged that. The key phrase in her own discussions of the war had now become "the decisive battle for the defense of the homeland".

 
Administrative Order Number 1: Operation Olympic, to Accompany Field Order No. 1 (August 12, 1945)

Administrative order number 1 covers the logistics and supply responsibilities for IX Corps for Operation Olympic, the invasion of Japan.

 
Report of Reconnaissance, Southern Kyushu: IX Corps Zone of Operation, Olympic (Majestic) Operation. (12-15-1945)

By Headquarters, IX Corps

 Abstract: At the direction of the Commanding General IX Corps, a terrain reconnaissance and survey of Japanese dispositions was made during period 3-5 December 1945 within the IX Corps zone for Operation Olympic (Majestic) on Southern Kyushu. The purpose of this mission was to determine the practicability of FO 1, Headquarters IX Corps, 12 August 1945, and the conditions of terrain which would have influenced the execution thereof. The findings of this study are contained herein. Sections include source of information, Japanese plan of operations, Japanese order of battle and equipment, and terrain reconnaissance.

 
Weather and the Occupation of Northern Japan (March 1946)

By Commander, Third Amphibious Force Chief of Naval Operations, Aerology Section

Abstract:  The planning for Operation OLYMPIC had included detailed consideration of expected weather in relation to all phases of amphibious operation, the shift from an assault landing in force to an occupation in several phases introduced a new trend into weather planning. Weather related to air support, use of smoke to secondary importance.

 
Planning the Defeat of Japan: A Study of Total War Strategy (1961)

By Lt. Col. Henry G. Morgan, Jr.; prepared in the Office of the Chief of Military History

 
Operation Downfall: The Devil Was in the Details (1995)

An Article from the National Defense University, Institute for National Strategic Studies.