The Allied decision to invade and capture the three major islands of the southern Marianas was made with three main objectives in mind. First, it was hoped that the enemy fleet or a sizable part of it might be flushed and decisively defeated. Second, the islands of Saipan, Tinian, and Guam were considered desirable as forward naval bases, even though they were not favored with first-rate harbors. But most important, the southern Marianas were ideally located for use as bases from which the newly developed very long range bombers could bombard the Japanese homeland. The islands were, as the wartime phrasemakers put it, "anchored aircraft carriers" from which the aerial war against Japan could be pressed with hitherto unequaled intensity.
The first of these objectives was of course achieved with Spruance's victory over Vice Adm. Jisaburo Ozawa's Mobile Fleet in the Battle of the Philippine Sea. Although a large part of the Japanese Fleet escaped destruction because of Spruance's determination not to leave the landing force at Saipan unprotected, the battle was nevertheless a decisive victory for the Americans. Sustaining only minor losses, the U.S. Fifth Fleet and its supporting submarines sank three carriers and two fleet tankers and damaged two carriers, a battleship, three cruisers, and a tanker. Equally if not more important were the tremendous losses of planes and trained aircraft personnel suffered by the enemy. All together, 476 Japanese planes were destroyed in the Battle of the Philippine Sea, and the total number of aviators lost was about 445.1
In the words of Professor Samuel Eliot Morison, "The Battle of the Philippine Sea contributed as much to victory as if Ozawa's fleet had been destroyed; for without its air arm the fleet was crippled, and the six carriers that survived were useful only as decoys . . . ."2 Fleet Admiral King was of the same opinion. Commenting on the affair long after the war, he wrote:
Spruance accomplished more lasting results than he or anyone else realized at the time, for the great loss of Japanese naval aircraft in the Battle of the Philippine Sea crippled Japanese naval aviation for the remainder of the war. Planes could be replaced, but pilots could not, and, as was discovered later in the year at the Battle for Leyte Gulf, the Japanese no longer had the trained and seasoned aviators that were necessary for successful operations against our fleet.3
The second objective of the campaign--to provide secondary naval facilities for the
LST'S, LCI'S, SMALL BOATS, and other vessels at Tanapag Harbor carried much of the shipping required by the stepped-up tempo of action in the Pacific in May 1945.
fleet--began to be realized shortly after the islands were secured. At the time of their capture, none of the southern Marianas possessed adequate sites for fleet anchorages, and, in fact, the only truly protected anchorage in the entire area was Apra Harbor at Guam. Nevertheless, on both Saipan and Tinian it did prove feasible to set up various other naval facilities important to the further prosecution of the war in the central Pacific. On Saipan, a naval seaplane base was constructed at Tanapag Harbor, small-boat and LVT repair units were established, and the pier at Garapan was enlarged to permit its employment as a major ammunition dock. Farther inland, naval construction battalions built a large tank farm to house aviation gasoline and diesel and fuel oil, a naval supply depot, sundry administration buildings, several hospitals, fleet recreation areas, and an ammunition depot. On Tinian, an airfield was constructed for the use of naval patrol planes, and a tank farm similar to that on Saipan was built. In addition, two railways were set up for use in landing craft repair, and Tinian Harbor was dredged and supplied with docking facilities for eight Liberty ships.4
Guam, with its relatively large land mass and protected harbor, was to be the scene of more ambitious base development
projects. On 9 August, the day before the official announcement that the island was "secured," Admiral Nimitz made known his plans to use Guam as a base for the Pacific Fleet and as forward headquarters for his Pacific Ocean Areas command.5 As a result, Apra Harbor was dredged and given the additional protection of a lengthy breakwater. An extensive tank farm was erected, several major supply depots were established, and hospitals and administration buildings were constructed. Early in 1945 Nimitz' forward headquarters was set up on the island, and by the end of the war the naval base at Guam was capable of supporting a third of the U.S. Pacific Fleet.6
The major construction effort on all three islands was of course devoted to laying out airfields and other facilities for the very long range bombers, the Army Air Forces' B-29's. In the minds of many U.S. strategic planners this had been, after all, the compelling reason for launching the Marianas Campaign. The first B-29 airdrome to be completed was Isely Field on Saipan.7 Work started on 24 June 1944 and by mid-December Saipan boasted two B-29 runways plus storage space for sixty spare bombers at nearby Kobler Field. The first of the very heavy bombers arrived on the island on 12 October, and on 24 November B-29's flew the first mission against Tokyo.8
On Tinian, two fields were developed. The first, North Field, on the site of the old Japanese airdrome near Marpi Point, was ready for use by February 1945, and the second, West Field, just above Tinian Town, became operational the next month. On Guam, North and Northwest Fields, located inland of Ritidian and Pati Points, respectively, were put into operation between January and June of 1945, and the first mission from Guam to Japan was launched in late February. In addition on Guam, Harmon Field above Agana was commissioned for use as headquarters of the XXI Bomber Command.
Starting on 24 November 1944 and continuing through early August of 1945 when the atomic bombs were dropped on Hiroshima and Nagasaki, the home islands of Japan were subjected to a mounting crescendo of B-29 raids, all flying out of the five airfields in the Marianas. Japan's industrial plants were flattened, her shipping was mined and sunk, and her cities were laid waste.
Without attempting to allocate responsibility for the ultimate defeat of Japan among the various agencies, services, and weapons that contributed to that end, it is more than clear that the Marianas-based B-29's played a major role. Certainly, that was the opinion of many responsible Japanese leaders. Prince Fumimaro Konoye later reported, "Fundamentally, the thing that brought about the determination to
HARMON FIELD, GUAM, where headquarters of the XXI Bomber Command opened, 16 December 1944.
make peace was the prolonged bombing by the B-29's." According to Premier Kantaro Suzuki: "It seemed . . . unavoidable that in the long run Japan would be almost destroyed by air attack so that merely on the basis of the B-29's alone I was convinced that Japan should sue for peace."9
Even before the bombs began to drop, many Japanese were aware that the loss of the Marianas, and especially of Saipan, was a crucial, if not the decisive, turning point in the war. The most immediate repercussion was the fall of Premier Tojo and his entire cabinet. Japanese leaders were aware of the tremendous potentialities of the B-29 (although not of the atomic bomb), and they fully realized that with the loss of the Marianas those potentialities could be quickly brought to bear against Japan. Prince Naruhiko Higashikuni, Commander in Chief of Home Defense Headquarters, later stated:
The war was lost when the Marianas were taken away from Japan and when we heard the B-29's were coming out . . . . We had nothing in Japan that we could use against such a weapon. From the point of view of the Home Defense Command, we felt that the war was lost and said so. If the B-29's could come over Japan, there was nothing that could be done.10
Postwar testimony in the same vein was volunteered by such high ranking officers as Fleet Admiral Nagano, Chief of the Naval General Staff and Supreme Naval Advisor to the Emperor; Vice Adm. Shigeru Fududome, who had served as Chief of Staff, Combined Fleet, Comnander, Second Air Fleet, and Commander, 10th Area Fleet; Vice Adm. Shigeyoshi Miwa, Commander in Chief, Sixth (Submarine) Fleet; and Capt. Mitsuo Fuchida, Air Staff Officer to the Commander in Chief, Combined Fleet.11
The Japanese high command had realized from the beginning the strategic importance of the Marianas in the Empire's defensive system. It was for that reason that the high command ordered the Combined Fleet to intercept or frustrate the landing on Saipan. The thorough defeats that Japan suffered during the Marianas campaign on the sea, on land, and in the air proved irreparable.
To be sure, other battles remained to be fought before the Japanese could finally be induced to surrender. General MacArthur's return to the Philippines would cut Japan's vital line of communications to the Netherlands Indies and secure important naval and air bases. The U.S. Navy's victory in the Battle of Leyte Gulf would reduce to virtual impotence the remnant of the Japanese Fleet that was left afloat after the Battle of the Philippine Sea. The capture of Iwo Jima by Admiral Nimitz' forces would greatly facilitate the bombing of the home islands from bases in the Marianas. And, finally, the successful invasion of Okinawa would bring American forces to the very doorstep of Japan.
Out of the long sequence of campaigns and battles that took place in the Pacific between 7 December 1941 and 15 August 1945, it is of course impossible to isolate any single one as "decisive" in bringing about the defeat of Japan. But certainly, by any reasonable standard of judgment, the campaign in the Marianas must be
rated high in the order of events that led to the success of American arms. Admiral King often spoke of the Marianas as "the key to the Pacific War."12 Purists might quarrel with his choice of the definite article, but few would deny that victory in the Marianas was a key and a very important key to the door that led to the defeat of the Japanese Empire in World War II.13
In the campaign in the Marianas, the U.S. Army played an important, although not the major, role. The Army contributed two reinforced divisions, a corps of artillery, and sundry other troops, numbering 39,280 officers and men. In addition, the Seventh Air Force provided three squadrons of P-47 fighters, a detachment of P-61 night fighters, and a squadron of B-25 medium bombers to fly tactical missions in support of the ground troops. By comparison, the Marine Corps contributed 85,824 officers and men--or three reinforced infantry divisions, a provisional brigade of two regiments, a corps of artillery, and various other troops.14
Army casualties came to 4,523 killed in action, dead of wounds, and wounded in action. Of these, 3,666 were incurred on Saipan and Tinian, 857 on Guam. Total Marine Corps casualties came to 19,272 killed in action, dead of wounds, and wounded in action. Of these 10,437 took place on Saipan, 1,892 on Tinian, and 6,943 on Guam.15 The ratio of casualties to total troops employed was roughly 1 to 9 for the Army and 1 to 4.5 for the Marine Corps. The higher proportion of casualties suffered by the Marine Corps can be explained largely by the fact that the marines were given the initial task of assaulting the beaches on all three islands, were in action for a longer time than either of the two Army infantry divisions, and were almost solely responsible for the fighting on Tinian.
The role of the Navy in the Marianas campaign was of course fundamental. Admiral Spruance's Fifth Fleet softened up the targets and kept the battlefields isolated once the troops were ashore. Naval vessels transported the troops to the islands, supplied them when they got there, and kept up a continuous program of naval bombardment against enemy troops and installations. Naval aircraft provided the great bulk of aerial support both before and during the land battles.
Without doubt the outstanding feature of the campaign in the Marianas was the skillful manner in which the separate services and the component arms of the U.S. forces were co-ordinated. Perhaps more than any other type of warfare, amphibious operations require a harmony of action, a precise meshing of the multitudinous gears that comprise the whole of the assault machinery. Land, sea, and air forces must be combined in the proper quantities at the proper time and place.
By the summer of 1944, the U.S. Army, Navy, and Marine Corps had had sufficient experience in joint operations to be optimistic about the success of future landings in the Pacific. Victory in the Marianas brought confirmation to the belief that current amphibious doctrine was sound and could be employed, with modifications, against any Japanese-held island or land mass.
To be sure, all was not perfection. There were still some "bugs" in the machinery, some failures of performance. Also, the Smith versus Smith affair on Saipan was alarming to those who had hoped for perfect teamwork between the services. Nevertheless, the relief of General Ralph Smith and the interservice controversy that ensued should not be allowed to obscure the fact that for the most part co-operation between the separate U.S. services was excellent. Had it been otherwise, victory in the Marianas would have been neither so rapid nor so complete.
1. Morison, New Guinea and the Marianas, p. 321.
2. Ibid., p. 318.
3. King and Whitehill, Fleet Admiral King, p. 559.
4. Department of the Navy, Bureau of Yards and Docks, Building the Navy's Bases in World War II: History of the Bureau of Yards and Docks and the Civil Engineer Corps, 1940-1946, 2 vols. (Washington, 1947), II, Ch. 28.
5. CINCPAC-CINCPOA Ser. 000650, 11 Aug 44. 44.
6. Bureau of Yards and Docks, Building the Navy's Bases in World War II, II, Ch. 28, The War Reports of General of the Army George C. Marshall, Chief of Staff, General of the Army H. H. Arnold, Commanding General, Army Air Forces, Fleet Admiral Ernest J. King, Commander-in-Chief, United States Fleet, and Chief of Naval Operations (Philadelphia & New York, J. B. Lippincott Company, 1947), p. 685.
7. For reasons unknown, the XXI Bomber Command changed the original spelling to Isley, although the field derived its name from Comdr Robert H. Isely, USN, a navy pilot who had been killed during the assault on Saipan. (See Craven and Cate, AAF V, p. 515.)
8. Information on the construction of B-29 bases in the Marianas is derived from Craven and Cate, AAF V, pp. 512-25, and Bureau of Yards and Docks, Building the Navy's Bases in World War II, II, Ch. 28.
9. AC/AS Mission Accomplished: Interrogations of Japanese Industrial, Military, and Civil Leaders of World War II, Washington 1946, pp. 19-40.
10. AC/AS Mission Accomplished, p. 18.
11. USSBS, Interrogations, II, Naval Nos. 80, 115, 72, 99.
12. King and Whitehill, Fleet Admiral King, p. 557.
13. See Butow, Japan's Decision to Surrender, passim.
14. These figures are derived from TF 56 Rpt FORAGER, Incl A, G-1 Rpt, pp. 3-23; Ibid., Incl C, G-3 Rpt, pp. 8-9; NTLF (TF 56.1) Rpt Marianas, Incl C, G-1 Rpt, pp. 2-5.
15. These figures are to be understood as approximate only. Casualty statistics submitted by various units are so uneven and at times so contradictory as to render impossible an absolutely precise statement of the number. The figure here given are derived from studies, made by the Marine Corps Historical Branch, G-3, U.S. Marine Corps Headquarters, which contain the most accurate and up-to-date data available. They are contained in Hoffman, Saipan, App. III, p. 268-69; Hoffman, Tinian, App. III, p. 150; Lodge, Guam, App. III, pp. 178-80.