Dan enlisted in the Navy in 1942, received his wings in 1943 and went to sea duty aboard the escort carrier Ommaney Bay in 1944. He provided extensive air support to ground troops piloting a TBF Avenger during the invasion of Pelau and the Battle of Leyte Gulf. Several times his plane was badly shot up and his gunner wounded once. They were credited with a probable kill on a Japanese plane. They saw it go down in flames but did not see it hit the water. He turned Japanese battleship away from his task force with a torpedo. He was credited with a probable hit. He also scored direct bomb and rocket hits which took out a Japanese destroyer. For his service he was awarded the Air Medal and the Distinguished Flying Cross. After the Ommaney Bay was sunk by a Kamikaze pilot, he became a flight instructor in operational training and torpedo bombing in Jacksonville, FL until the end of the war.