In the Pacific Theater, a force of six Japanese fleet carriers with their combined aircraft striking power, the "Kidō Butai", acted as a unit and roamed virtually at will for the first six months of the war. It made destructive raids against enemy positions from Hawaii in the east to India in the west and effectively supported Japanese invasions of the American Philippines, British Malaya and Burma, and the Dutch East Indies. Between May and October 1942, however, Japan and America fought four major battles between fleets centered around their aircraft carriers. During these battles, opposing warships never came within sight of each other nor fired their guns at other warships. Aircraft alone did the attacking. The first of these battles thwarted the Japanese attempt in the Coral Sea to isolate Australia. The second halted the expansion of Japanese control eastward in the Pacific toward Midway Island. The next two helped sustain the American presence on Guadalcanal. These four engagements were costly for both sides. At the time Pearl Harbor was attacked, Japan had a total of nine fleet and light carriers in the Pacific Theater. America had four in the Pacific with another two far away in the Atlantic. At the end of October 1942, after battle attrition from sinkings and damages, Japan had only three such carriers operational in the Pacific Theater and America, for a two-week period, had none. Though costly,the battles were strategically advantageous for the Americans, contributing significantly to the shift of strategic initiative in the Pacific Theater from Japan to America.