After sweeping across Maritime Southeast Asia in the months following Pearl Harbor, Japan looked to further expand its territory, taking control of the Solomon Islands and parts of New Guinea. In May 1942, American and Australian forces defeated the Japanese in the Battle of the Coral Sea, prompting a Japanese land campaign across the island of New Guinea. Seeking to seize control of a strategically-placed island and destroy the U.S. fleet in the Pacific, Japan also launched an attack on the American-held Midway Atoll. With the assistance of the Magic cryptanalysis project, Admiral Chester Nimitz led an American force that defeated the Japanese navy at the Battle of Midway. The Battle of Midway resulted in the Japanese fleet's loss of four crucial aircraft carriers, and the battle marked a major reversal of fortune in the Pacific War. In August 1942, the United States launched an invasion of the Japanese-held South Pacific island of Guadalcanal in the Solomon Islands; Japanese and American forces contested control of Guadalcanal until February 1943. After the Battle of Guadalcanal, the U.S. adopted an island hopping strategy in order to avoid entrenched Japanese garrisons. By early 1944, Allied forces had established control over much of New Guinea and had landed on the adjacent island of New Britain.