War in the Pacific (1941-1945)

The impact of The War in the Pacific was felt in varied ways, and to varied degrees, across the many Islands. Ultimately, its culmination would mark the end of the Japanese Period and the start of the USN Period.

Start

After Pearl Harbor, Japan's rapid movement south and eastward into the Pacific revealed the extent to which military preparations had been undertaken and operations projected which included the use of the mandated islands as bases for aggression.

The capture of Guam on 10 December 1941 by the Japanese solidified their hold in the Micronesian area which formed a natural strategic barrier of islands from which Japanese power was applied throughout the Pacific.

The first major break in this island barrier came in 1943, by which time United States and Allied forces had gathered enough strength to start their historic westward movement. A succession of key islands were taken by military occupation and used as stepping stones from which to launch attacks upon Japanese installations closer to the Japanese homeland and finally upon the homeland itself. Each captured island was fortified, and airstrips and military and naval installations built to make it a spring board for further operations, thus steadily weakening the military power of the Japanese.

Island Bases

At this time the only islands wanted were those which were best suited for rapid construction of military installations, so that those islands with better natural advantages were selected for occupation. A natural harbor was necessary, as time did not permit the construction of large-scale breakwaters or excessive dredging operations. Along with good landing facilities, sufficient flat terrain was essential to permit the rapid construction of large airfields and other shore based military installations; usually, indeed, the Japanese already had airfields at such points.

The islands chosen had also of necessity to be large enough to afford space for the building of housing for large numbers of troops and to furnish storage space for the vast amount of equipment needed for the successful prosecution of the war. And last but by no means least, the islands selected had not to be so well protected and defended by the Japanese that the cost of taking them would overshadow their value in their future use as bases for advanced operations. Thus a great many islands including some of the strongest Japanese bases were bypassed and never were occupied until after the formal surrender of the Japanese.

Marshall Islands

The early campaigns of the Japanese forces had reached almost to the continent of Australia, so that it was necessary to first recapture islands for bases in the Solomons, New Guinea, New Britain, and the Gilberts. After the taking of Tarawa and Makin in the Gilberts, the next step was to move northwestward into the Marshalls, the first of the Japanese territories proper. The first islands occupied in the Marshalls were Kwajalein and Majuro, on 31 January 1944. Then followed Enewetak on 19 February 1944. These three islands, especially Kwajalein with its enormous lagoon and anchorages, provided excellent points from which to mount attacks upon the adjacent islands in the territory.

Marianas

After the three bases in the Marshalls were completed the next step was to establish bases in the Marianas. The Marianas were close enough to Tokyo to allow nonstop bombing raids from them to any point in the Japanese homeland. The first island occupied was Saipan, which was taken by combined Army, Navy, and Marine Corps forces on 15 June 1944. The next step was to recapture Guam. The assault started on 21 July and the island was completely recaptured by 10 August 1944. During the period of the attack on Guam the island of Tinian was also occupied, starting on 24 July 1944. From these three islands in the Marianas, secured only after costly and bitter fighting, the B-29 air raids on Japan were staged.

Western Carolines and Palau

In order to make projected future attacks on the Philippines easier, bases for operations had to be taken in the Western Carolines and Palau. Hence, Peleliu of the southern end of the main Palau group was taken on 15 September 1944, Angaur, the adjacent phosphate island, on 17 September 1944, and Ulithi, the atoll northeast of Yap having a spacious lagoon anchorage, on 23 September 1944.

The islands listed here were the only ones which were captured within the mandate prior to the formal surrender of the Japanese nation. A great many other islands were subjected to heavy air bombing and shelling by naval vessels. Although bombings and shellings were carried out only on the fortified islands such as Chuuk, Yap, Pohnpei, and the northern Palaus, all the islands in the area suffered, due to the disrupted economy caused by the complete blockade of Japanese shipping in the entire mandated area. After the surrender of the Japanese on 2 September 1945, the rest of the islands were occupied or visited as quickly as circumstances permitted.