From 1943 onwards, hard-fought campaigns at the battles of Buna-Gona, the Tarawa, the Philippine Sea, Leyte Gulf, Iwo Jima, Okinawa, and others resulted in horrific casualties, mostly on the Japanese side, and produced further Japanese retreats. Very few Japanese ended up in POW camps. This may have been due to Japanese soldiers' reluctance to surrender. The Battle of Okinawa was the bloodiest battle of the Pacific War. The total number of casualties shocked American military strategists. This made them apprehensive to invade Japan's main islands, because it would result in a very high death toll. The brutality of the conflict is exemplified by US troops taking body parts from dead Japanese soldiers as "war trophies" or "war souvenirs" and Japanese cannibalism.