<P> As a result of several key improvements in strategy and tactics, from 1943, Allied submarines waged a more effective campaign against Japanese merchant shipping and the IJN, in effect strangling the Japanese Empire of resources . By the end of the war in August, 1945, U.S. Navy submarines sank around 1300 Japanese merchant ships, as well as roughly 200 warships . Only 42 U.S. submarines were sunk in the Pacific, but 3,500 (22%) submariners were killed, the highest casualty rate of any American force in World War II . The force destroyed over half of all Japanese merchant ships, totaling well over five million tons of shipping . </P> <P> As victory for the United States slowly approached, casualties mounted . A fear in the American high command was that an invasion of mainland Japan would lead to enormous losses on the part of the Allies, as casualty estimates for the planned Operation Downfall demonstrate . President Harry Truman gave the order to drop the first atomic bomb on Hiroshima on 6 August 1945, hoping that the destruction of the city would break Japanese resolve and end the war . A second bomb was dropped on Nagasaki on 9 August after it appeared that the Japanese high command was not planning to surrender . Approximately 140,000 people died in Hiroshima from the bomb and its aftereffects by the end of 1945, and approximately 74,000 in Nagasaki . </P> <P> V-J Day which occurred on 15 August 1945 marked the end of the United States' war with the Empire of Japan . Since Japan was the last remaining Axis Power, V-J Day also marked the end of World War II . </P> <P> The United States contributed several forces to the China Burma India theater, such as the 5307th Composite Unit (Provisional) but nicknamed "Merrill's Marauders" after its commander; Frank Merrill, it was a United States Army long range penetration special operations jungle warfare unit organized as light infantry assault units . In slightly more than five months of combat in 1944, the Marauders advanced 750 miles through some of the harshest jungle terrain in the world, fought in five major engagements, mostly behind enemy lines, with or in support of British Empire and Chinese forces in Burma and suffered many casualties . On 10 August 1944 the Marauders were consolidated into the 475th Infantry . The U.S. also had an adviser to Chiang Kai - shek and Joseph Stillwell . Units of the Tenth Air Force, Fourteenth Air Force, and Twentieth Air Force of the USAAF also served in the theatre, including the previously mentioned "Flying Tigers". </P>

Who implemented the world war ii military strategy described in the text