In the early part of his career Frankel served in the USS Trenton (CL-11) Augusta (CA-31), Chester (CA-27), and Chaumont (AP-5). Following this sea duty, he was Russian language student in Riga, Latvia, 1936-1938. He then served in the USS Ellet (DD-398) as gunnery officer and XO. He was Assistant Naval Attaché, Moscow, and Assistant Naval Attaché for Air, Murmansk-Archangel – service in connection with Lend-Lease shipments to the Soviet Union, directing repairs to U.S. vessels, salvaging stranded and abandoned vessels, and supervising hospitalization and repatriation of survivors. He served on the staff of CinCPac and as officer in charge, Joint Intelligence Center Pacific Ocean Area; Assistant Chief of Staff, CinCPac; Deputy Director for Security, ONI; Deputy Director, Naval Intelligence; and Chief of Staff, DIA, from 1961 until his retirement in 1964.