The American invasion of the Japanese stronghold of Saipan in the western Pacific was an incredibly brutal battle, claiming 55,000 soldiers' and civilians' lives in just over three weeks in the summer of 1944. The U.S. Marines spearheaded the amphibious landing, encountering a fierce and well-prepared resistance from the Japanese troops who controlled the commanding heights looming over the beach.

Artillery, snipers and automatic weapons took a deadly toll with casualties mounting under the remorseless barrage. Marines later commented on the precision of the Japanese mortars and artillery fire. A battalion caught out in the open took heavy casualties as it desperately tried to dig in and find shelter, with one of its officers recalling: "it's hard to dig a hole when you're lying on your stomach digging with your chin, your elbows, your knees, and your toes. ... (But) it is possible to dig a hole that way, I found." Such was a precarious beachhead established on the first day of the invasion.

The amphibious landing at Saipan drew on the lessons of previous conquests in Tarawa in November 1943 and the Kwajalein and Eniwetok atolls in the Marshall Islands in early 1944. Next up was the Mariana Islands of Guam, Saipan and Tinian, part of the island-hopping campaign adopted by the U.S. that struck deeper into the Japanese defenses, bypassing some well-fortified islands and cutting off their supply lines. Saipan was almost equidistant from the Marshall Islands and Japan, nearly 2,100 km, putting much of the archipelago within B-29 bomber range.