Guarding the eastern approaches to the southern Philippines, the Palau Islands were developed by the Japanese, in conjunction with Truk, into a powerful naval base. After the virtual neutralization of Truk by repeated Allied air attacks, the Palau Island replaced it as the principal Japanese advance naval base and assumbly point for fuel, ammunition, and supplies moving between Japan and the southwest Pacific. The islands had alos been developed as advance airbases to support light, medium and heavy aircraft, in the forthcoming Philippines operations.

    The Palau Islands, which lie about 540 miles due east of Davao, are among the westernmost islands of the Carolines. The group is actually a complex atoll, made up of a cluster of volcanic islands, fragmented coral atolls, and islands of limestone composition, the whole surrounded by reefs. Peleliu and Angaur, at the southernmost tip of the group, were the only islands developed by our forces.

    Angaur, 2½  miles in length and less than 2 miles wide, rises 15 to 20 feet above sea level. The island is densely wooded, and the soil is generally coral limestone, so hard that it hindered construction. There is only one sheltered water area, a small boat basin on the western side of the island.

    Peleliu is 5½ miles long and 2½ wide. The major portion of the land is low and level, but the central and northern portions contain numerous high rock ridges. Swamp areas, extending north and south, divide the island except for a minor strip on which ist single east-west road is built. The coastline is mostly rocky but has about 2 miles of scattered sandy beaches.

    Although the Palau group offers a spacious and well-protected anchorage for major fleet elements, no major Japanese facilities existed for construction or repair of any except small craft. There were three airfields in the Palau group, the largest of which was located on Peleliu. A new operational strip was on the small island of Ngesebus, just north of Peleliu and connected to it by a bridge in the last stages of construction. A third field was still under construction at Airai, near the southern end of Babelthuap Island.

    The Peliliu airfield, a cleared area at the southern portion of the island, contained two runways in an X pattern, one 3,900 feet and the other 3,850 feet long. There were two sizable service aprons, connected with each other, and with turning circles, by hard-surfaced taxiways. Good roads lined the northern coastal areas with the airfield.

    Three days of surface bombardment and air bombing preceded the landing on Peleliu. During this time, mine sweepers cleared the waters of Peleliu and adjacent Angaur Island, and underwater demolition teams removed beach obstacles. The landing, on September 15, 1944, was made by units of the First Marine Division, Despite Difficult reef conditions, the initial landings were successful, and the troops quickly overran the beach defenses, which were thickly mined but less heavily manned than expected. By the night of the 16th, the Pelelio airfield, which was the prime objective of the entire operation, had been captured. After the rapid conquest of the southern portion of the island, however, progress on Peliliu slowed, as the rough ridge which formed the north-south backbone of the island was a natural fortress of mutually supporting cave positions. Although these were surrounded by September 26, it was not until the middle of October that the assault phase was complete.

    The 81st Infantry Division went ashore on Angaur Island, 6 miles south of Peleliu, on September 17. Beach conditions here were more favorable than at Peliliu, and opposition also was less severe. By September 20, the entire island had been overrun, with the exception of a small inland area.

    Marines from Peliliu landing on Ngesebus Island, just north of Peliliu, on September 28, by a shore-to-shore movement, and light enemy opposition was overcome by September 29. Later, several small islands in the vicinity were occupied as outposts. From Peleliu and Angaur, the other islands were dominated; enemy forces were neutralized.

    Three Seabee groups participated in the initial landing on Peleliu, the 33rd and 73rd Battalions and Construction Battaltion Detachment 1054. On D-Day, the two construction battaltion assigned men of the shore parties to assist in unloading supplies and ammunition and to aid in burying the dead. Unloading operations were made extremely difficult by the lack of harbors and the nature of the reef.

    CBD 1054 opearted the 24 pontoon barges with propulsion units. These pontoon barges were used extensively in the Peliliu invasion to transfer cargo between various types of landing craft, and to serve as floating dumps for high-priority cargo. On D-Day-plus-three, CBD 1054 installed pontoon causeways to the outer reef, and the next day the first LST wa sbeached and unloaded over them. Causeway sections were also used to ferry loads of mobile equipment from LST’s.

    On D-Day-plus-four, the 33rd Battalion commenced removing land mines, duds, and shell fragmesnts from the airfield, and when the frirst construction equipment came ashore the next day, it was immediately put to work filling shell holes and making general repairs. The strip was placed in operation 72 hours after the first equipment began work, when three squadrons of fighters arrived to support the remainder of the operation.

    On September 23, the 33rd Battalion began construction on Peleliu of a bomber strip, 6,000 feet long, with additional equipment borrowed from the First Marine Engineer Batttalion and the 73rd Construction Battalion. Land mines were encountered, and during the first six days the field was subjected to mortar fire, but 24-hour air operation began on the seventh day.

    Airfield development continued during the early months of 1945. When completed, the bomber strip measured 6,000 by 300 feet, and the fighter runway, 4,000 by 250 feet. Taxiways and parking areas were constructed to support the assigned seven squadrons and 100 transient and cargo planes.

    The Seabees also erected four quonset-type warehoused for aviation shops, 20 quonset huts for offices and repair facilities, and complete camp installations for aviation personnel.

    By January 1945, the 73rd Battalion had completed a tank farm, consisting of one 10,000-barrel tank for motor gasoline, twenty 1,000-barrel tanks for aviation gasoline, and three 1,000-barrel tanks for the diesel oil.

    Hospitals constructed by the Seabees were the 17th Army Evacuation Hospital and Navy Base Hospital 20. The former had a 440-bed capacity and was completed by the 73rd Battalion in November 1944. The 33rd Battalion then started construction of the naval hospital, and by the end of December, six H-type quonset-hut units, of 100 beds each, had been completed with all facilities. Due to delay in the arrival of materials, the 320-bed annex to Base Hospital 20 was not completed until March 1945. Numerous dispensaries, with a total capacity of 161 beds, were also provided for various naval activities.

    By the end of January 1945, minor waterfront facilities were complete. The 33rd had rebuilt a Japanese concrete-block pier, which provided berths for three light craft. The approach channel was dredged to a 10-foot low-water depth and an LCT landing beach prepared.

    The 301st Battalion, a harbor reclamation unit, was brought in to dredge access channels to a small boat basin, and to provide sufficient maneuvering space for small craft at all stages of the tide. A marine railway and shops for small-boat repair were built by the 73rd.

    Stevedoring was handled by the first section of the 17th Special Battalion, with the assistance of crews from the 73rd Battalion.

    Three major supply centers had been established by early 1945. Construction of the supply depot, begun by Army Engineers, was taken over by the 33rd Battalion in December 1944. Eight quonset-type warehouses, with concrete floors, were built for this activity. For the aviation supply depot, the Seabees constructed five quonset buildings. At the airfield, four 20-by-50-feet steel magazines were erceted. The spare parts depot conssted of four quonset buildings, with concrete floors and unloading platforms, and several quonset huts for offices. More than 16 miles of primary roads were built to serve these activities on Peleliu.

    Angaur was developed as an Army base, the airfield being constructed by two Army engineer battalions. Installations for the field were an airstrip, 7,000 by 150 feet, adequate taxiways, and hardstands for 120 planes. CBMU 532, which reported at Angaur in October 1944, assisted the Army by the erection of quonset-hut camps for aviation personnel.

    The construction program for Angaur was not an extensive one. Detachments of Seabee units stationed on Peliliu were sent to Angaur to hadnle the erection of a tank farm, to assist the Army in the construction of the 39th Station Hospital, and to develop waterfront facilities.

    During late 1944, the 73rd Battalion sent men to Angaur to build the tank farm, comprising twelve 1,000-barrel tanks for aviation gasoline, two 10,000-barrel diesel-oil tanks, and five 1,000-barrel tanks for motor gasoline. The existing phosphate pier was used to carry the pipe line for the tank farm. The project was completed by February 1945. A small boat basin was developed by a detachment of the 301st Battalion, just south of the phosphate loading pier on the western side of the island, and the harbor was dredged to provide a minimum depth of 6 feet at low tide. A natural coral breakwater, forming the wester side of the boat haven, was improved on the basin side by the construction of a concrete deck. Pontoon strings were used to form the southern end of the basin. This section was, in effect, a 70-foot pier which could furnish barge berths on the basin side.

    The 73rd Battalion built boat shops and a 30-ton marine railway, 130 feet long.

    At Blue Beach, one officer and fifteen men of CBD 1054 were assigned to the construction of a pontoon causeway. The installation consisted of two single-pontoon strings, 150 long,  placed about 150 feet apart at right angles to the beach line. A 2-by-30-pontoon string was then placed at right angles to the offshore end of the first two strings. The enclosed space was filled with coral rock, sand, and gravel, after all sections had been filled with sand and sunk. The pier was ready for use by LCT’s on November 1, 1944.

    In June 1945, the Army air base was abandoned. CBMU 532 took charge of dismantling and crating salvageable structures; they were secured on July 11, 1945.