On this day, Japanese forces on Guadalcanal Island, defeated by Marines, start to withdraw after the Japanese emperor finally gives them permission. On July 6, 1942, the Japanese landed on Guadalcanal Island, part of the Solomon Islands chain, and began constructing an airfield. In response, the U.S. launched Operation Watchtower, in which American troops landed on five islands within the Solomon chain, including Guadalcanal. The U.S. forces quickly met their main objective of taking the airfield, and the outnumbered Japanese troops temporarily retreated. Japanese reinforcements were landed, though, and fierce hand-to-hand jungle fighting ensued. When the U.S. Navy supplied reinforcement troops, the Americans gained the advantage. By February 1943, the Japanese retreated on secret orders of their emperor. In fact, the Japanese retreat was so stealthy that the Americans did not even know it had taken place until they stumbled upon abandoned positions, empty boats, and discarded supplies. In total, the Japanese lost more than 25,000 men compared with a loss of 1,600 by the Americans.