How a remote lagoon and a 'secret weapon' allowed the US Navy to overwhelm Japanese forces during...

On September 16, 1944, as US Marines began a major assault on Peleliu, Adm. William Halsey, commander of the US Navy's 3rd Fleet, ordered III Amphibious Corps to seize Ulithi Atoll, located 400 miles to the northeast.

Seven days later, soldiers from the 81st Infantry Division began landing on Ulithi's coral islets. The Japanese had abandoned the atoll a few months earlier, and the US landing was unopposed. Within two days the Americans had completed their initial unloading operations.

Located roughly between Guam and Palau and some 1,300 miles from Tokyo, Ulithi would have been easy to overlook, but within a few weeks it would become essential to the war effort.