Planners feared that the eventual invasion of Japan would be even more costly. Two of the bloodiest battles were on Iwo Jima and Okinawa, the first of the Japanese “Home Islands.” Both were fought in 1945, collectively costing nearly 20,000 lives. The closer the Americans got to shores of Japan, the more fierce and costly the conflicts became. Following a strategy known as “Island Hopping,” American troops moved inexorably closer to the Japanese “Home Islands.” As they went, they set up airfields and support bases that helped them expand further and further into the Pacific. Since mid-1942, the United States had been executing a slow and bloody campaign against the Japanese Imperial forces. The United States had entered in December of 1941 after the surprise Japanese attack on Pearl Harbor. By 1945, the Second World War had been dragging on for six long years.