The Philippines were an important US base until the Japanese forced the surrender of US forces in April 1942. This led to the infamous Bataan Death March where thousands of Filipino and US prisoners of war died. In the Pacific Theater, the Doolittle Raid on Tokyo and the Battles of the Coral Sea and Midway turned the tide in favor of the US by stopping Japanese naval advances. The US also fought major battles to take Iwo Jima and Okinawa to reach the Japanese mainland. Meanwhile, the Manhattan Project developed the atomic bomb which the US dropped on Hiroshima and Nagasaki in August 1945 after Japan refused to surrender, leading to their surrender and the end of the war.