Genaust served in the Pacific Theater during World War II and was posthumously awarded the Bronze Star Medal with Combat "V" and Purple Heart Medal in September 1945, for heroic actions using a rifle in a firefight on Saipan where he was wounded on July 9, 1944. He was recommended for the Navy Cross by Norman Hatch, his photo section commander, but the nomination was turned down because Genaust was a cameraman and not an infantryman. He also shared in the Navy Presidential Unit Citation awarded to the 4th Marine Division for the Battle of Saipan and Tinian (June 15 – August 1, 1944). It took eight months for Genaust to recover from his leg wound he obtained on Saipan. He was given the opportunity to return home, but instead he volunteered to go to Iwo Jima.