FILE - In this April 1944 file photo, infantrymen of the U.S. Army Americal Division watch from behind a barricade of piled-up sandbags as U.S. dive bombers blast Japanese positions, right, across the mouth of the Torokina river on the island of Bougainville in Papua New Guinea. The island is where American fighters shot down Admiral Isoroku Yamamoto, the mastermind of the Pearl Harbor attack, making the wreck site one of most important of World War II. Now, 75 years later, a group from the U.S. and Japan is trekking to the remote Pacific island to document the site. (AP Photo, File)