In September 1942, Nevers enlisted at age 39 in the United States Marine Corps; he was given the rank of captain. In the spring of 1943, he was stationed at the Olds Gunnery School in Lansing, Michigan. While Nevers was stationed at a Marine base in Santa Barbara, California, his wife became ill with pneumonia; she died in a San Francisco hospital in July 1943. Nevers left for the South Pacific theater of World War II in October 1943. In April 1944, he was reported by the Associated Press to have been stationed for the past several months with a marine amphibious unit in the Pacific. In October 1944, Nevers returned to San Francisco after spending 10 months in charge of ground personnel with a squadron in the South Pacific. In December 1944, while stationed at Naval Station Treasure Island in San Francisco, Nevers was promoted to the rank of major. In February 1945, he became the athletic officer at the Marine Corps base in San Diego.