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Introduction World War II was the largest and most violent armed conflict in the history of mankind. However, the half century that now separates us from that conflict has exacted its toll on our collective knowledge. While World War II continues to absorb the interest of military schol- ars and historians, as well as its veterans, a generation of Americans has grown to maturity largely unaware of the political, social, and military implications of a war that, more than any other, united us as a people with a common purpose. Highly relevant today, World War II has much to teach us, not only about the profession of arms, but also about military prepared- ness, global strategy, and combined operations in the coalition war against fascism. During the next several years, the U.S. Army will participate in the nation’s 50th anniversary commemoration of World War II. The commemoration will include the publication of various materials to help educate Americans about that war. The works pro- duced will provide great opportunities to learn about and renew pride in an Army that fought so magnificently in what has been called “the mighty endeavor.” World War II was waged on land, on sea, and in the air over several diverse theaters of operation for approximately six years. The following essay is one of a series of campaign studies highlighting those struggles that, with their accompanying suggestions for further reading, are designed to introduce you to one of the Army’s significant military feats from that war. This brochure was prepared in the U.S. Army Center of Military History by Charles R. Anderson. I hope this absorbing account of that period will enhance your appreciation of American achievements during World War II. GORDON R. SULLIVAN General, United States Army Chief of Staff Western Pacific 15 June 1944–2 September 1945 By the summer of 1944 American forces in the Pacific had established two routes of attack in their drive toward Japan. In the Central Pacific Navy and Marine Corps units, with Army assistance, were “island-hopping” westward from Hawaii, taking the Gilbert Islands in a costly campaign in November 1943 and the Marshall Islands in January–February 1944. In the South and Southwest Pacific Areas, Army units, with Navy and Marine Corps support, had taken Guadalcanal and Bougainville in 1942–43 and, operating with Australian forces, had cleared northeast New Guinea and the Hollandia area of Netherlands New Guinea by May 1944. These vic- tories brought American forces to the inner defense line of the Japanese Empire. In deciding where to breach that line, the Allies looked for a place that would not only puncture Japanese confidence but provide anchorages for naval support of subsequent operations and air bases for strikes against enemy industrial and military instal- lations. The best islands for these purposes lay in the Western Pacific: the Marianas and the Palaus. Strategic Setting When United States Army and Navy forces began pushing west into the Pacific after the disaster at Pearl Harbor, they had their ulti- mate objective, the Japanese home islands, clearly in mind. However, they lacked any detailed list of preliminary objectives that would bring them to the enemy’s shores. Each island victory raised anew the ques- tion of the next intermediate goal. By the summer of 1944 the Allies faced a number of choices in the Pacific. They could continue directly west from Hawaii on a Central Pacific thrust that had just won them the Marshall Islands. They could continue toward the Philippines on a Southwest Pacific course that had recently won New Guinea. Or they could continue operations along both of these axes simultaneously. During 1943 influential personalities in the U.S. Army and Navy lined up behind different strategies for the Pacific. The Chief of Naval Operations, Admiral Ernest J. King, favored focusing Allied efforts against Japan in a thrust westward from Hawaii. Seconded by Admiral Chester W. Nimitz, Commander in Chief, Pacific Ocean Areas and Pacific Fleet, King argued that his Central Pacific strategy also repre- 120° 140° THE PACIFIC AND ADJACENT THEATERS 60° UNION OF SOVIET 1941–1944 SOCIALIST REPUBLICS Japanese Limit of Control 0 1600 Miles at the Equator 80° 100° USSR MANCHURIA MONGOLIA 40° KOREA C H I N A A T I B E T J NEPAL BHUTAN Iw I N D I A FORMOSA BURMA Hong Kong 20° SOUTHWEST PACIFIC AREA 2 42 N4 SOUTH LUZON G U THAILAND PHILIPPINES U J CHINA A FRENCH INDOCHINA SEA N U MINDANAO J NORTH PALAU BORNEO ISLANDS C MALAYA W A K S S A R A CENTRAL P 0° UM SingaporeBORNEO CELEBES A JUN T R I N D I A N A NETHERLANDS INDIES NEW G 2 4 O C E A N JAVA AU G PA MAY 42 SOUTHEAST ASIA COMMAND 20° A U S T R A L I 80° 100° 120° 140° 160° 180° 160° USSR BERING S E A 60° A U G 4 2 (cid:1)Attu S D N M ALEUT I A N I S L A A Y 4 2 N NORTH PACIFIC AREA CENTRAL PACIFIC AREA A 40° 2 4 N P U P A C I F I C J A O C E A N (cid:1) Battle of Midway MIDWAY wo Jima ISLANDS HAWAIIAN ISLANDS (cid:1) MARIANA Wake Pearl Harbor Strike 20° ISLANDS A MARSHALL U ISLANDS G Guam 4 2 44 N U Truk CAROLINE ISLANDS (cid:1)Makin (cid:1) PACIFIC AREA Tarawa BISMARCK GILBERT SOUTH PACIFIC AREA 0° N42 ARCHIPELAGO ISLANDS UINEA SOLOMON MAY 42 APUA ISLANDS ELLICE (cid:1) (cid:1) ISLANDS Guadalcanal (cid:1) C Battle O of R A Coral Sea L NEW FIJI S HEBRIDES ISLANDS E A A NEW TONGA ISLANDS 20° CALEDONIA 160° 180° 160° sented the most direct route to the Philippines and would, at the same time, place American forces on the enemy line of communications between Japan and the oil-rich East Indies. King repeated his Central Pacific proposal at the Trident Conference in Washington in May, but it was neither approved nor rejected. King’s major opponent was General Douglas MacArthur, the Allied Southwest Pacific theater commander. MacArthur agreed on the need to return to the Philippines but not via the Marshalls and Marianas. Instead, he proposed a Southwest Pacific strategy: an exten- sion of his own command’s operations in New Guinea, which would push Allied forces westward through Morotai and then northward into the Philippines. A series of Allied planning conferences in 1943 failed to resolve the issue. The strong identification of each strategy with a different military service—Central Pacific with the U.S. Navy and Southwest Pacific with the U.S. Army—tended to undermine an unbiased appraisal of either course of action and to encourage the potentially dangerous pursuit of both with inadequate resources. Finally, toward the end of 1943, a technological development began to influence the issue. The Army Air Forces announced the imminent appearance of a new long-range bomber, the B–29. The new weapon strengthened the Central Pacific strategy, since the island chain particularly desired by Admiral King—the Marianas—lay 1,270 miles from Tokyo, comfort- ably within the 1,500-mile radius of the new aircraft. At the second Cairo Conference in December 1943 the Allies thus approved seizure of the Marianas, tentatively scheduled for October 1944. Subsequent operations along this axis would include seizure of the Palaus to secure the flank for the turn northwest into the Philippines. Although these decisions gave priority to the Central Pacific strategy, they did not amount to a rejection of MacArthur’s Southwest Pacific proposals. In fact, the Joint Chiefs of Staff reaffirmed in March 1944 that the advance toward Japan would continue on both the Central and Southwest Pacific axes. At the same time, unexpectedly rapid success in the Marshalls allowed planners to advance the assault on the Marianas from October to June. Operations Located some 3,300 miles west of Hawaii and 1,400 miles east of the Philippines, the Marianas archipelago consists of fifteen volcanic islands. The Marianas already had a long history of foreign domina- tion before the Japanese arrived to incorporate the archipelago and its 6 Chamorro people into a new imperial order. First held by the Spanish since the late seventeenth century, then, except for Guam, passed to the Germans in 1899, the islands were taken by the Japanese during World War I, an occupation ratified by the Treaty of Versailles. Even before they left the League of Nations in 1935, the Japanese had begun fortifying the Marianas. By the 1940s the islands stood as a keystone in the defensive line around the Japanese Empire. The Imperial Japanese Navy exercised theater control over the Marianas and surrounding seas through its Central Pacific Area Fleet, commanded by Vice Adm. Chuichi Nagumo, leader of the Pearl Harbor strike force. The Imperial Japanese Armycontrolled all ground forces in the Marianas through its 31st Army, commanded by Lt. Gen. Hideyoshi Obata. Major subordinate commands were the 43d Division on Saipan and the 29th Division on Guam. Although both units were understrength, having lost several troop transports to American sub- marines, both were also augmented by a number of independent battal- ions and naval landing units. Japanese forces in the Marianas, both Imperial Armyand Navy, totaled about 59,000 men. The Marianas campaign expanded United States Army operations in a theater commanded by the U.S. Navy. Admiral Nimitz assigned overall campaign responsibility to Vice Adm. Raymond A. Spruance’s Fifth Fleet. Vice Adm. Richmond Kelly Turner would command the Joint Expeditionary Force charged with the amphibious assault. Turner himself would also command directly a Northern Attack Force against Saipan and Tinian, while a Southern Attack Force under Rear Adm. Richard L. Conolly would assault Guam. Vice Adm. Marc A. Mitscher’s Fast Carrier Task Force and Vice Adm. Charles A. Lockwood’s Submarine Force, Pacific Fleet, would cover all landings. Lt. Gen. Holland M. Smith, USMC, Commanding General, V Amphibious Corps, would control the Marianas amphibious forces as each left U.S. Navy control at the water’s edge. Three Marine Corps general officers would command the landing forces on the targeted islands: Holland Smith on Saipan, Harry Schmidt on Tinian, and Roy S. Geiger on Guam. Amphibious units assigned to the Marianas included the 2d, 3d, and 4th Marine Divisions and a sepa- rate Marine brigade. Three major Army units—the 27th and 77th Infantry Divisions and XXIV Corps Artillery—were assigned from U.S. Army Forces in the Central Pacific Area, commanded by Lt. Gen. Robert C. Richardson, Jr. Army and Marine Corps units totaled 106,000 men. Naval support for this huge force included 110 trans- port vessels and auxiliaries and 88 fire support ships, from rocket gunboats to aircraft carriers. 7 SAIPAN I TINIAN I AGUIJAN I ROTA I SOUTHERN MARIANAS 1944 APPROXIMATE CONTOUR INTERVAL 300 FEET 0 30 Miles GUAM Saipan The Marianas archipelago spans 500 miles from north to south. American planners chose their objectives from among the more heavily fortified islands at the southern end of the chain—Saipan, Tinian, Rota, and Guam. First targeted was Saipan, large enough at fifteen miles long by seven miles wide to allow combined arms maneuver. Inland hill masses dominated sandy beaches, with two prominent 8 Aerial view of Saipan, July 1944.(National Archives) ridgelines framing a central valley planted in sugar cane. For invasion forces the major terrain features derived from the volcanic origin of the island. Unlike the low and generally flat surface of coral islands, the terrain of Saipan presented a confusion of heavily jungled and jagged but low cliff faces, rock outcroppings, sinkholes, and caves often as difficult to see as to walk over and around. The highest peaks were the volcanic cones whose eruptions formed the island: Mount Nafutan, 407 feet, to the southeast; Mount Kagman, about the same height, on the east coast; Mount Marpi, 833 feet, at the northern tip; and Mount Tapotchau, rising 1,554 feet on the west side of the central valley. A small population, most of which the Japanese had enlisted in sugar cane farming, resided in three west coast villages: Charan Kanoa, near the south end of the island; Garapan at mid-coast; and Tanapag, six miles from Marpi Point. A prime subject of War Ministry reinforcement for more than a decade, Saipan was well fortified by 1944. Preassault American aerial photographs identified 231 artillery pieces and 270 machine gun posi- tions. The Japanese had one airfield—Aslito Field—in use in the south and another under construction at Marpi Point. Defending forces included over 25,000 Japanese Army troops and over 6,000 naval per- 9 U.S. reinforcements wade ashore from LSTs off Saipan. (National Archives) sonnel. Besides ample artillery and modest aircraft support, these forces could call on an armored regiment of forty-eight tanks. Lt. Gen. Yoshitsugu Saito commanded both the 43d Division and the entire Saipan defense force. The small size of Saipan dictated a straightforward plan of assault. The 2d and 4th Marine Divisions would land on the southwest coast and stake out a beachhead. Joined by elements of the 27th Division, the corps would advance to the east coast, splitting enemy defenders into the northern half and southeast corners of the island. Army troops would clear the latter, then join the two Marine divisions for the drive north to Marpi Point. Admiral Spruance set the invasion date at 15 June. In the weeks before American troops crossed its beaches, Saipan was subjected to intense naval gunfire and air “softening up.” Beginning in February Admiral Mitscher’s fast carriers turned their air squadrons loose on Saipan and nearby islands in daylight raids; on 13 June they were joined by battleships and other surface ships firing con- tinuously on Saipan and Tinian until D-day. Just before dawn on D-day surface ships alternated with bombers and fighters in saturating the landing beaches as troop-carrying landing craft approached the shore- 10