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5. Naval Actions The major threat to the beachhead established by the marines on Bougainville would not come from the Japanese army units there. General Hyakutaki was very slow to react to the lodgment at Cape Torokina, and even had he been more concerned, the terrain, weather, and lack of roads on the island would have prevented an immediate counterattack in force. Any significant Japanese counterthrust would come from the sea. As Admiral Wilkinson had surmised the Japanese, once alerted to the invasion, would muster all their available naval and air forces and attempt to isolate the invaders by destroying the transports, cargo vessels, and the covering naval force. This conclusion had led to his decision to land the two marine regiments abreast as quickly as possible and to have the transports unloaded and out of the bay by nightfall of D day. Admiral Koga, commander of the Combined Fleet, the bulk of which was at Truk, was in many ways a prisoner of his and his predecessor's obsession with a great final battle with the main U.S. fleet units. He believed he should husband the bulk of his naval force in a central locale to be able to respond to such a challenge, which he believed would come in the Central Pacific, not the South Pacific area. Aside from his preconceptions, he had very real problems. It was apparent by the fall of 1943 that the United States fleet had recovered from the devastating Pearl Harbor strike and that Admiral Nimitz was preparing to carry out offensive operations, probably in the Marshall Islands. Another inescapable fact was the severe damage done to the Japanese fleet at the Coral Sea, Midway, and the Guadalcanal naval engagements. By the close of 1942 Japan had lost six carriers and Naval Actions 79 seventeen destroyers. Action by u.s. surface and air units and particularly submarines in the three months prior to the Kolombangara action had destroyed over a quarter of a million tons of shipping.1 There was no possibility that Japanese shipyards could replace those ships, and the portents for future actions were even more devastating for Japan. All these conditions supported Koga's decision to husband his air and surface power in the Central Pacific. Admiral Kusaka from his vantage point at Rabaul saw the situation differentlyfrom the planners at Imperial Headquarters in Tokyo and at Combined Fleet Headquarters at Truk. Vice Admiral Shigeru Fukudome , Koga's chief of staff, later recalled that Admiral Koga, conforming to the defensive posture earlier agreed upon, had refused repeated requests from Rabaul for reinforcements. He insisted that Kusaka make do with what force he had in hand. Yet the air actions with Kenney's 5th Air Force and those related to the Allied occupation of the central Solomons had so reduced the air strength at Rabaul that something had to be done to try and wrest air control over New Britain from the Americans. Koga decided to send a total of approximately 250 planes from the five carriers of Admiral Jisaburo Ozawa's Air Fleet. Koga specifically stated that the bulk ofthese were on only a tenday loan, and presumably after the situation had been stabilized they were to return to the main fleet. The invasion of Bougainville upset these plans, occurring just before the planes were scheduled to return. As Admiral Fukudome noted, although the planes were not originally to be used in such offensive operations, Kusaka "justcouldn't stand by and not employ them." 2 Similar confusion in strategy and tactics could be seen in the Japanese utilization of surface units. Koga had no intention of committing his carriers and heavy units to the defense of Rabaul. Failing major reinforcements prior to the Bougainville landings, Admiral Kusaka, who had commanded all 8th Fleet units in the South Pacific since February, had to counter the actions of the American naval forces supporting General MacArthur and at the same time those of Admiral Halsey operating in the Solomons area, and he simply did not have the ships available for both. Furthermore, there had been few opportunities for the crews of the various ships at Rabaul to train together, especially for night maneuvers. At Bougainville, however, the key factor in the Japanese responses was the lack of good intelligence reports that would have given the planners at Rabaul the necessary information to intercept the Empress Augusta Bay task force. The first reaction to the impending invasion came at 1000 on 31 [3...

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