Dennis joined the Lighthouse Service in 1940 and the entered the US Coast Guard. Served in the North Atlantic where patrolled and engaged in rescue missions; convoyed destroyers to Newfoundland, transported troops to England and D-Day operations and Operation Dragoon. Pacific Theatre battles include Guadalcanal, Tulagi, Iwo Jima and Okinawa. Transported troops to the US and post war weather patrol in the North Atlantic. Resigned from the Coast Guard in 1946. Postwar career in the Civil Service at Melville, Quonset Point Naval Air Station, NUWC and the Naval Reserve.