Lapham is credited for bringing the perilous situation of the 513 Allied POWs and internees remaining in the Cabanatuan Japanese POW camp to the attention of the American forces then fighting their way across Luzon towards Manila in January 1945. The POWs, captured after the fall of Corregidor and Bataan in 1942, had not been shipped to Japan because they were considered too ill or unfit. Lapham's was concerned the POWs would be executed before the camp could be liberated. His concerns were well justified given the August 1944 Japanese War Ministry directive to commandants of POW camps outlining the final disposition of prisoners (known as the "August 1 Kill-All Order"), and the killing of 139 American POWs by the Japanese at Palawan, Philippines on 14 December 1944. Lapham's efforts lead to a rescue mission on January 30, 1945, by 121 members of the US Army's 6th Ranger Battalion, and two teams of Alamo Scouts, who marched behind enemy lines, eliminated the Japanese forces securing the camp, liberated its 513 prisoners and returned them to American lines.