in the impending war were to "[eject] British and American strength from the Netherlands Indies and the Philippines, [and] to establish a policy of autonomous self-sufficiency and economic independence." The Empire of Japan accomplished its initial strategic objectives in the first six months of the war, capturing Hong Kong, the Philippines, Thailand, Malaya, Singapore, the Dutch East Indies, Wake Island, New Britain, the northern Gilbert Islands, and Guam. A Japanese goal was to establish an effective defensive perimeter from British India on the west, through the Dutch East Indies on the south, and to island bases in the south and central Pacific as its southeastern line of defense. Anchoring its defensive positions in the South Pacific was the major Japanese army and navy base at Rabaul, New Britain, which had been captured from the Australians in January 1942. In March and April, Japanese forces occupied and began constructing an airfield at Buka in northern Bougainville, as well as an airfield and naval base at Buin, in southern Bougainville. Japanese advance into the Solomons In April 1942, the Japanese Army and Navy together initiated Operation Mo, a joint plan to capture Port Moresby in New Guinea. Also part of the plan was a Navy operation to capture Tulagi in the southern Solomons. The objective of the operation was for the Japanese to extend their southern perimeter and to establish bases to support possible future advances to seize Nauru, Ocean Island, New Caledonia, Fiji, and Samoa and thereby cut the supply lines between Australia and the United States, with the goal of reducing or eliminating Australia as a threat to Japanese positions in the South Pacific. The Japanese Navy also proposed a future invasion of Australia, but the Army answered that it currently lacked enough troops to support such an operation. Japanese naval forces captured Tulagi but its invasion of Port Moresby was repulsed at the Battle of the Coral Sea. Shortly thereafter, the Japanese Navy established small garrisons on the other northern and central Solomon Islands. One month later, the Japanese Combined Fleet lost four of its fleet aircraft carriers at the Battle of Midway. The Allies countered the threats to Australia by a build-up of troops and aircraft, with the aim of implementing plans to approach and reconquer the Philippines. In March 1942 Admiral Ernest King, then Commander-in Chief of the U.S. Fleet, had advocated an offense from New Hebrides