At this point, the JCS decided that seizure of Rabaul would be unnecessarily costly. An air base in the Admiralties would support the westward drive along the north coast of New Guinea and support Central Pacific advances by long-range air reconnaissance; the Admiralties would also provide a major naval base for the Fifth Fleet of the Central Pacific. Despite the changed plans the seizure of western New Britain began on 15 December 1943 when Army units landed at Arawe, followed by a Marine landing at Cape Gloucester on 26 December. In mid-February 1944, New Zealand troops of Halsey's command took an air base on one of the Green Islands, east of Rabaul, and at the end of the month MacArthur's forces tightened the circle on Rabaul by landing in the Admiralty Islands. These islands eventually provided two heavy bomber fields as well as two fields for carrier-type planes, and Seeadler Harbor was developed into one of the largest naval bases in the Pacific.
In the following three months Marine and Army forces completed the encirclement, and effectively isolated the 100,000-man Japanese garrison at Rabaul. This operation set the pattern of Allied operations in the Pacific for the rest of the war. Frontal attacks against strong Japanese positions were avoided if possible. Rather, Allied forces "leap-frogged" toward Japan, their leaps limited only by the range of land-based aircraft and the availability of carrier-borne planes. Bypassed Japanese positions were thereby left isolated and strategically impotent.
Advancing on Two Fronts toward the Philippines
With the Philippines as a prime objective, the Allies used two routes of advance. The first went through the central Pacific Area via the Gilberts, Marshalls, Marianas, Carolines, and Palaus. The other through the Southwest Pacific Area via the north coast of New Guinea. Once the Marianas were taken, it would be possible to use them as bases from which the new long-range B-29 Superfortress bombers could strike at the heart of Japan. An advantage of the second route urged by MacArthur was that it would provide for land-based air cover along the way. The double-pronged advance had the merit of keeping Japanese forces divided and of providing opportunities for surprise.
The advance through the Central Pacific got under way in the Gilberts when Marines landed on Tarawa on 21 November 1943 and took the island in a four-day fight with 3,000 Marine casualties. Army troops overwhelmed the small Japanese garrison on Makin between 20 and 24 November 1943. The Japanese did not react strongly to the loss of the Gilberts, and at the end of January 1944 Nimitz' Army and Marine forces moved into the eastern and central Marshalls to seize Majuro and Kwajalein and on 17 February Marine and Army units landed on Eniwetok Atoll in the western Marshalls. Concurrently, Nimitz conducted a long-awaited carrier strike against Truk in the central Carolines, considered Japan's key bastion in the Central Pacific. Anticipating the attack, the Japanese had partially withdrawn from Truk and the capture of the atoll, set for June, no longer appeared necessary. Nimitz then drew up plans to invade the Marianas in mid-June and move on to the western Carolines and Palaus in mid-September, accelerating the pace of the advance. MacArthur's progress in New Guinea was also ahead of schedule and supported plans for an early move against the Philippines.
Biak and the Battle of the Philippine Sea
On 12 March 1944 the Joint Chiefs of Staff rearranged the schedules of advance of both prongs of the Pacific Theater directing MacArthur to plan for the invasion of Luzon and Nimitz to plan for the invasion of Formosa early in 1945. MacArthur's ground force made continued progress along northern New Guinea creating airstrips within striking distance of the Japanese Navy, assembling in Philippine waters before moving into the Central Pacific for the anticipated confrontation in the Marianas.
The key was Biak Island, assaulted by MacArthur on 27 May. An American-controlled Biak was an unacceptable threat to the Japanese flank, so they risked major elements of their fleet and land-based air strength to send strong reinforcements to Biak in an attempt to block MacArthur's forces, strength they would soon miss at the Battle of the Philippine Sea.
The U.S. Pacific Fleet arrived in the Marianas just as the Japanese were about to launch agianst Biak. The Japanese hastily reassembled their naval forces and sailed northwestward into the Battle of the Philippine Sea (19-20 June 1944) where the unprepared and unsupported Japanese suffered another shattering naval defeat, a defeat which assured the success of the invasions of both Biak and the Marianas. It also again demonstrated that the U.S. Pacific Fleet's carrier task forces were the decisive element in the Pacific war.
On the Doorstep of the Philippines
Army and Marine divisions under Nimitz landed on Saipan in the Marianas on 15 June 1944, on Guam on 21 July, and on Tinian Island 24 July. The American seizure of the Marianas at last brought Japan itself within reach of the U.S. Army Air Forces' B-29 bombers, which began to fly missions against the Japanese homeland in late November 1944.
MacArthur's forces continued to gain ground in New Guinea during June through August and with the capture of Morotai Island on 15 September moved half way up the island chain from New Guinea to the Philippines. At the same time, Nimitz's Marines captured Peleliu and nearby islands, virtually completing the approach to the Philippines, providing the airfields and anchorages needed to support the invasion. In seven months MacArthur's forces had moved forward nearly 1,500 miles from the Admiralties to Morotai while in ten months Nimitz' forces had advanced over 4,500 miles from Hawaii to Peleliu.
Invasion of the Philippines
In mid-September 1944, air strikes against the Philippines found unexpectedly weak Japanese air cover and few signs of significant ground or naval activity. MacArthur and Nimitz proposed to the Joint Chiefs a move directly to Leyte in October, bypassing Mindanao, with MacArthur invading Leyte 20 October 1944. The Japanese rushed ground, sea and air reinforcements to prevent MacArthur from gaining a foothold, but to no avail. The climactic air-naval Battle of Leyte Gulf virtually eliminated the Japanese Navy as a factor in the Pacific war. With the Leyte beaches secure, U.S. Army units proceeded to destroy the Japanese ground forces, although Japanese troops in the mountains of northwestern Leyte continued organized resistance well into the spring of 1945.
MacArthur's forces moved on to Luzon with the seizure of an air base in southwestern Mindoro, 150 miles south of Manila, on 15 December 1944, and the invasion of Luzon itself on 9 January 1945, when four Army divisions landed along the shores of Lingayen Gulf. Army units reached Manila on 3 February and took another month of bitter building-to-building fighting to root out the Japanese. Organized Japanese resistance ended by late June 1945 except for a strong pocket in the mountains of north central Luzon.
MacArthur kept all available naval and air forces busy with Leyte and Luzon through February 1945, delaying other plans and cancelling any move on Formosa, no longer necessary. The Iwo Jima assault finally took place on 19 February 1945, with the 3d, 4th and 5th Marine Divisions, supported by minor Army elements, making and reinforcing the landings. The Marines overcame fanatic resistance from firmly entrenched Japanese, who held what was probably the strongest defensive system American forces encountered during the Pacific war. It took a month of bloody fighting to secure the island. By early March crippled B-29's were able to make emergency landings on Iwo and by the end of March an airfield was fully operational for fighter planes. Later a heavy bomber field and another fighter base were constructed on the island.
The last amphibious operation of the war involved an Australian division who went ashore at Balikpapan, Borneo on 1 July.
Final plans for the defeat of Japan envisaged gradual tightening of the ring by blockade and bombardment from the Marianas, Philippines, and Ryukyus with an invasion of the home islands to be mounted from these bases. In the end, the invasion was unnecessary due to the stunning impact of the atomic bombs used against Hiroshima (6 August) and Nagasaki (9 August). The Japanese surrendered 2 September 1945 on the battleship USS Missouri (BB-63), anchored in Tokyo Bay.
Recommended Books about the Pacific Theater of Operations
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