"Tokyo rocks under the weight of our bombs...I want the entire world to know that this direction must and will remain - unchanged and unhampered, Our demand has been and it remains - unconditional surrender."
- President Truman, in his initial address to Congress, 16 April 1945.
On 8 May 1943 the American Joint Chiefs of Staff (JCS) approved a broad plan for future operations in the war against Japan. Entitled the "Strategic Plan for the Defeat of Japan," the plan aimed at securing control of the South China coast, and the islands of Luzon and Formosa. These areas were needed to develop air bases from which to bomb Japan and sever her supply lines.(1) The memorandum also stated, "The United Nations war objective is unconditional surrender of the Axis Powers. The accomplishment of this objective may require the invasion of Japan." This is the earliest official mention of the possibility of an invasion of the Japanese homeland.(2) There were two principal commanders with the responsibility of executing U.S. war plans in the Pacific. General Douglas MacArthur, USA, as Commander-in-Chief Southwest Pacific Area (CINCSWPA), operating in the South Pacific, and Admiral Chester Nimitz, USN, as Commander-in-Chief Pacific Ocean Areas (CINCPOA), operating in the Central Pacific. General MacArthur's campaign in New Guinea, and Admiral Nimitz's drive across the Pacific to take the Caroline and Marshall islands during 1943 and early 1944 were steps in the strategic plan to take Luzon, Formosa and the South China coast. However, throughout the summer and autumn of 1944 military planners in Washington argued over the timetable and priority of the Luzon and Formosa operations. There were not enough troops or ships in the Pacific to conduct both operations simultaneously. On 3 October 1944 the Joint Chiefs of Staff decided on the priorities of the strategic plan. They directed General MacArthur to invade Luzon and dropped Formosa as a target in the plan.(3) Instead of an assault on Formosa, Admiral Nimitz was directed to secure the islands of Iwo Jima and Okinawa as advance bases in support of the air campaign against Japan.(4)
The first half of 1945 saw MacArthur and Nimitz executing the U.S. strategic plan. In January 1945, six Army Divisions of the U.S. Sixth Army, commanded by General Walter Krueger, invaded Luzon in the Philippines.(5) The battle for Luzon would last longer than six months. On 1 July 1945, the exhausted Sixth Army was relieved by the Eighth Army to allow the divisions of the Sixth Army time to prepare for future operations against the Japanese home islands.
In the western Central Pacific, the V Amphibious Corps, comprised of the Third, Fourth and Fifth Marine Divisions, assaulted Iwo Jima on 16 February 1945. The island was declared secure by the end of March and the three Marine divisions withdrew to their training bases in the Marianas and Hawaii. The third campaign identified by the JCS in its October 1944 directive began on 1 April 1945, when the Tenth Army comprised of seven divisions assaulted Okinawa. The island was not secured until three months later, on June 21. The ferocity of the Japanese defenders on Iwo Jima and Okinawa convinced American policymakers that Japan would not surrender unconditionally until she was decisively defeated at home.
Decision to Invade the Homeland
After successful landings on Luzon in January 1945, military planners began to seriously analyze the task of invading the Japanese home islands. The Army Chief of Staff, General George C. Marshall, and most Army leaders believed that an invasion was necessary to bring about Japan's unconditional surrender. However, Admiral Ernest King, Chief of Naval Operations, and General Hap H. Arnold, Army Air Forces Chief of Staff, believed that Japan was on the verge of collapse and that a continued naval and air blockade and bombardment, would produce Japan's surrender. In late April 1945, just one week after Truman reiterated what had been Roosevelt's policy of unconditional surrender, an intelligence report prepared for the Joint Chiefs of Staff warned that unconditional surrender could not be forced upon the Japanese before the middle or latter part of 1946 without a land campaign on the Japanese home islands.(6) Therefore, in April 1945, at the height of the Luzon and Okinawa campaigns, the Joint Chiefs of Staff instructed Admiral Nimitz and General MacArthur to make plans and preparations for an attack on Japan.(7) Admiral King opposed any landing in Japan; he was convinced that the Japanese Army had great advantages on their home islands, and only consented to the invasion after Admiral Nimitz recommended in favor of it.(8) On 25 May 1945, the JCS issued a directive to begin formal planning for the campaign, code-named "Operation Downfall," which was to force Japan's unconditional surrender. Operation Downfall was divided into two major operations, Operation Olympic, the invasion of the island of Kyushu to be executed in the fall of 1945, and Operation Coronet, the invasion of Honshu, scheduled for the spring of 1946.
On 18 June 1945, President Truman held a Japanese strategy meeting at the White House. At this meeting he was briefed by the Joint Chiefs of Staff on the elements of Operation Downfall. Truman's primary concern was on the number of casualties and whether an invasion of the home islands was necessary. General Marshall gave Truman an estimate of approximately 40,000 U.S. casualties for Operation Olympic.(9) After hours of discussion, Truman approved further planning for Olympic, with an execution date of 1 November 1945. Operation Coronet, if needed, would be conducted in March 1946.
The first stage of the invasion of the Japanese home islands would be the attack on Kyushu. This island, about twice the size of Massachusetts, with a population of 10 million was the southern most island of the Japanese archipelago. Kyushu, said a Shinto myth, was the wellspring of the Japanese people, the island where the gods walked, became mortal, and beget the divine Japanese race.(10) The Japanese ethic known as Bushido, the Way of the Warrior, was thought to have originated in Kyushu.(11) Kagoshima, a town in southern Kyushu, was the capital of the Satsuma clan. From the Satsuma samurai came the men who founded the Imperial Army in 1871 and shaped the course of modern Japan. Kyushu thus had a special place in the psyche of the Japanese Army and they were preparing to defend its sacred ground at whatever the cost.
The Joint Chiefs of Staff directed the invasion of Kyushu, with a target date of 1 November 1945, in order to:
(1) Intensify the blockade and aerial bombardment of Japan.
(2) Contain and destroy major enemy forces.
(3) Support further advance for the purpose of establishing the conditions favorable to the decisive invasion of the industrial heart of Japan.(12)
Since the term "D-Day" had become synonymous with the European Theater of operations landing at Normandy on 6 June 1944, "X-Day" was designated as the term for the day of the landing on Kyushu.
The initial assault would be conducted by eleven US Army infantry divisions and three Marine divisions, divided into four corps under the command of General Walter Krueger's Sixth Army: I Corps consisted of the Army's 25th, 33rd, and 41st infantry divisions; XI Corps, the Army's Americal and 43rd infantry divisions and the 1st Cavalry division; IX Corps, the reserve, the Army's 81st and 98th infantry divisions; and the V Amphibious Corps, the Second, Third, and Fifth Marine divisions. The number of ground forces to be landed in the first four days of the assault would total approximately 436,486. Follow-up forces would number 356,902. With air support personnel of 22,160, the numbers topped 800,000 for Operation Olympic.(13) Should it be found that the fourteen divisions allotted to the Sixth Army were insufficient to capture and hold southern Kyushu, that army would be reinforced at the rate of three divisions a month from X+30 by the units earmarked for Coronet.(14)
In comparison, the largest amphibious assault in the Pacific theater of operations to date was Okinawa, were 182,000 men assaulted the beaches. In the European theater, the largest amphibious assault occurred on Sicily, were 170,000 troops landed. The historic D-Day landing at Normandy in June 1944 had an assault force of 150,000 men. Olympic thus would be the largest amphibious operation in history. The area to be occupied in southern Kyushu totaled about 3,000 square miles.
Admiral Nimitz would be in command of all the naval forces. The operation would be the first time that the two major Pacific fleets, Admiral William F. Halsey's Third Fleet and Admiral Raymond Spruance's Fifth Fleet, operated together. The number of ships involved in Olympic would be the largest ever gathered for a military operation.(15) The invasion force would include 14 fast aircraft carriers, 6 light aircraft carriers, 36 escort carriers, 20 battleships and over 1,300 troop and cargo transports.
Thousands of land based fighters and bombers of the Far East Air Forces would provide air support for Olympic. The Far East Air Forces, under the command of General George C. Kenney, belonged to MacArthur and included the Fifth, Seventh and Thirteenth Air Forces. Also providing air support were the Fleet Air Wings based on the carriers, and the 1st, 2nd, 3rd, and 4th Marine Aircraft Wings (MAW) which were mostly land based. The MAWs would provide support in the amphibious phase under the control of Admiral Spruance's Fifth Fleet. Once established ashore on Kyushu the Marine Aircraft Wings would fall under the control of the Far East Air Forces.(16) Also included in the operation were the strategic bombers of the Twentieth Air Force, and the 20th and 21st Bomber Commands. The thousands of B-29s from the U.S. Army Strategic Air Force in the Pacific would be conducting strategic bombing of Japanese cities.(17)
The tactical plan of maneuver (see Map 3) for the Sixth Army would begin on 27 October 1945, X-5. On X-5, the 40th Infantry Division, reinforced, would land on Kuchino-Erabu Shima, Kuro Shima, Kusakaki Jima, Uji Gunto; all of these are islands and island chains southwest of southern Kyushu.(18) The 40th infantry division would secure these islands to provide air warning facilities to aid in the main landings. Simultaneously, the 158th Regimental Combat Team (RCT) was to be prepared to land on northern Tanega Shima, south of Kyushu, to destroy hostile forces and assist in clearing Osumi-Kaikyo. The 40th Division, on X-4 was to land in northern and southern Koshiki Retto to secure Nakakoshiki Wan, Nakagawara Ura and other areas suitable for the establishment of emergency anchorages, seaplane bases, and air warning stations.
On X-Day, simultaneous landings were to be effected at two points along the southeastern shore and at one point along the southwestern coast of Kyushu. The objective: to clear the southern end of Kyushu of enemy troops, thus permitting the use of Kagoshima Wan and Ariake Wan as major unloading ports. I Corps would land in the Yamazaki Matsusaki area of southeastern Kyushu, capture Miyazaki and Miyazaki Airfield and secure a corps beachhead, to include Fukushima on the south bank of Hitosuse-Gawa. XI Corps would land in the Shibushi-Kashiwabaru area of Ariake Wan, capture Shibushi and the Shibushi Airfield, and secure a Corps beachhead. V Amphibious Corps would land with two divisions in assault and one in reserve in the Kaminokawa-Kushikino area of southwestern Kyushu and establish a beachhead. IX Corps, Sixth Army reserve, would be prepared to reinforce other elements of the Sixth Army in the objective areas as directed, or to land on the south coast of Kyushu, west of Kaimon-Dake, on or after X+3. At the same time, the 158th RCT was to be prepared to reinforce elements of the Sixth Army as directed.
After its beachhead had been secured and when so directed by Sixth Army (see Map 4), I Corps was to advance inland and secure the general line Sadohara-Honjo-Tawao-Aoidake and to establish contact with XI Corps. XI Corps, meanwhile, was to advance inland and secure the general line Aoki-Iwakawa-Takakuma-Kanoya and to attempt to establish contact with I Corps. V Amphibious Corps, when directed, was to advance with a division toward Sendai and another division toward Kagoshima; it was to secure the general line Kagoshima-Kawakamicho-Ichiino-Sendai. All Corps were to establish communications facilities and to construct and improve roads and airfields as directed. The 11th Airborne Division and 77th Infantry Division, Sixth Army follow-on forces, were to have been prepared to reinforce elements of the Sixth Army on X+22.
An essential supporting feature of the tactical ground plan was the interdiction of enemy troop movements overland from North to South Kyushu; and interdiction of the movement of enemy troops to Kyushu from other main Japanese islands by tunnel or boat. Because the U.S. would enjoy air and naval superiority, interdiction of the Japanese reinforcements would be accomplished by air and ship bombardment.(19)
Deception was an integral part of Olympic strategy. Operation "Pastel Two" was a deception plan to deceive the Japanese of the true objective area of southern Kyushu. Limited amphibious landings were scheduled for 1 October 1945, on the Chinese coast to set up airfields from which to attack the home islands.(20) Planners hoped that the Japanese would believe that this move to the Chinese coast was the Allies main effort during the fall of 1945. Operation Pastel Two was to divert Japanese attention only temporarily, as planners anticipated that the landings on the southern islands off Kyushu, on X-4, would tip off the Japanese to the true landing areas. However, they believed that the Japanese would have little time to react to the landings especially given U.S. air and naval superiority.
In early May 1945 the Joint Planning Staff (JPS) of the Joint Chiefs of Staff had drafted two directives for Operation Olympic. The difference in the directives reflected disagreement between the Navy and War Departments over command of the operation. Navy planners assigned overall command of the invasion to Admiral Nimitz until the Army was established ashore, when it would transfer to General MacArthur. This was typical of the CATF/CLF relationship exercised throughout the Central Pacific drive under Nimitz. In contrast, the Army planners placed General MacArthur in command of the entire operation, including the naval and amphibious operations. For two weeks General Marshal and Admiral King could not come to an agreement on the wording of the final directive. General Marshall believed that there was a need to designate a commander with primary responsibility for the whole campaign. Admiral King felt that MacArthur's responsibility for the campaign in Kyushu should not include the amphibious assault.
The final wording for the directive was far from specific. The 25 May 1945 JCS directive limited MacArthur, Commander-in-Chief, US Army Forces, Pacific, to "primary responsibility for the conduct of Operation Olympic including control, in case of exigencies, of the actual amphibious assault through the appropriate naval commander."(21) Thus, Admiral Nimitz while retaining his role as Commander-in-Chief, Pacific Fleet and Pacific Ocean Areas, was to be responsible for the naval and amphibious phases of the operations. "Exigencies" were not defined or discussed in the directive. General Arnold, who controlled the Twentieth Air Force, was directed to "cooperate in the plans, preparations, and execution of Operation Olympic", but was not put under the command of one or the other of the theater commanders. The 20th Air Force would be placed under the control of the Strategic Air Force in the Pacific, commanded by General Carl A. Spaatz, who answered directly to the Joint Chiefs of Staff. From the initial planning stages, no unity of command would exist within the American forces.
Subordinate commanders who would lead the forces in the invasion were identified by June and their staffs commenced detailed planning of the operation. General Walter Krueger, Commander of the US Sixth Army, would command the ground forces in the assault. Admiral Kelly Turner would command the amphibious phase and General George C. Kearny would command the air support for the assault.
Operation Olympic, the largest planned amphibious assault in history, was scheduled for 1 November 1945. It was to be a strike into the Japanese home islands to secure advanced airfields and ports from which to support an invasion of the industrial heart of Japan. The landing on Kyushu would entail a simultaneous amphibious assault by nine infantry divisions. A third of the assault force would be comprised of the three Marine divisions of the V Amphibious Corps.
1. Ronald H. Spector, Eagle Against the Sun (New York: The Free Press, 1985), 418.
2. Jack K. Bauer, "Olympic vs. Ketsu-Go," Marine Corps Gazette, August 1965, 32.
3. Spector, Eagle Against the Sun, 419-420. A major Japanese offensive during the summer of 1944 along the southeast coast of China captured the airfields that U.S. planners were eyeing. The majority of Pacific commanders, including Halsey and Nimitz, supported MacArthur's advocacy of Luzon first. The Air Forces then began to look to the Marianas as the principle base for their B-29s to attack Japan.
4. ibid., 494. Actually, Nimitz was directed to occupy "one or more positions in the Nanpo Shoto," the long chain of islands extending 750 miles southward from central Japan. Iwo Jima was the only island group which possessed both landing beaches and suitable terrain for an airfield.
5. ibid., 419-420. JCS directed MacArthur to assault Luzon on 3 December 1944. However, the invasion was later changed to 9 January 1945 because of the slow progress of Sixth Army to secure Leyte and the airfields required to support the Luzon effort.
6. Thomas B. Allen, and Norman Polmar, Code-Name Downfall (New York: Simon and Schuster, 1995), 126.
7. Spector, Eagle Against the Sun, 541.
8. Spector, Eagle Against the Sun, 542.
9. White House, Minutes of 18 June 1945 Japanese Strategy meeting, 12.
10. Allen and Polmar, Code-Name Downfall, 221.
11. Meirion and Susie Harries, Soldiers of the Sun: The Rise and Fall of the Japanese Imperial Army (New York: Random House, 1991), 7.
12. General HQs, U.S. Army Forces in the Pacific (USAFPAC), Staff Study: Operation Olympic, 28 May 1945, 2.
13. General HQs, U.S. Army Forces in the Pacific (USAFPAC), Staff Study: Operation Olympic, 32.
14. S. Woodburn Kirby, The War Against Japan, Volume V (London: Her Majesty's Stationary Office, 1969), 155.
15. Many sources indicate that 4,800 ships and craft were used for the assault at Normandy in June 1944. This large number takes into account the landing craft and other small boats that were used to cross the English Channel. It is difficult to compare the operation at Normandy with the amphibious operations in the Pacific, because the assault at Normandy was primarily a shore-to-shore movement, whereas the operations in the Pacific where ship-to-shore movements.
16. Commander Amphibious Forces Pacific Fleet (ConPhibsPac), Operations Plan, No. A11-45, Annex A, 10 August 1945, 13.
17. Allen and Polmar, Code-Name Downfall, 147.
18. V Amphibious Corps, Appendix 3 to Annex C to Operation Report, Occupation of Japan, 30 November 1945, 31.
19. Commander Amphibious Forces Pacific Fleet (ConPhibsPac), Operations Plan No. A11-45, 10 August 1945, 10.
20. Stanley Weintraub, The Last Great Victory, The End of WWII July/August 1945 (New York: Truman Talley Books/Dutton, 1995), 313.
21. Grace Person Hayes, The History of the Joint Chiefs of Staff in WWII, The War Against Japan (Annapolis, MD. Naval Institute Press, 1982), 706.