at around this time to dispatch Implacable and several other recently arrived warships to attack the Japanese positions at Truk. The purpose of this operation was to ensure that the warships' crews had recent combat experience before the BPF commenced operations off Japan during July. Rawlings' initial orders for the attack specified that it was to involve two days of air strikes against Japanese airfields. The crews of the ships involved, including Implacables aircraft pilots, were not told that the main purpose of the operation was training. During the early years of the Pacific War, Truk Atoll in the Caroline Islands had been an important base for the Imperial Japanese Navy (IJN), using facilities which had been constructed there before the outbreak of hostilities. However, it was isolated by the rapid Allied advances in the Pacific during 1943 and early 1944, and ceased to be a significant base after being heavily attacked by the United States Navy's Fast Carrier Task Force during Operation Hailstone in February 1944. Nevertheless, the facilities at Truk could have potentially been used to raid the important Allied facilities which had been established in the Mariana Islands or the major US Navy anchorage at Ulithi. To prevent the islands from being used for this purpose, they were repeatedly attacked by US Navy aircraft carriers which were preparing to join the Fast Carrier Task Force and United States Army Air Forces heavy bomber units; like the British operation in June 1945, these raids were conducted to provide combat experience for the American airmen. The Japanese forces at Truk conscripted local civilians to rapidly repair the damage caused to airfields by these raids. The garrison's anti-aircraft units also fired upon all of the raids, though the scale of this resistance decreased over time. Opposing forces In mid-1945 the Japanese garrison at Truk remained large, but had no offensive capacity. As of May that year, the garrison comprised around 13,600 Imperial Japanese Army personnel commanded by Lieutenant General Shunzaburo Mugikura and 10,600 IJN personnel under Vice Admiral Chuichi Hara. A large number of coastal artillery batteries and anti-aircraft guns protected the islands, but no warships and only a small number of aircraft were stationed there. Radar stations on the islands provided warning of most incoming raids. The Japanese forces regarded Truk's air defences as inadequate even before the start of the Allied bombardment of the atoll. The Truk garrison