Following graduation from the Naval Academy in 1943, Long was in the crew of the battleship USS Colorado (BB-45) during Pacific combat. He completed submarine school, then served in a succession of diesel boats: USS Corsair (SS-435), USS Cutlass (SS-478), and USS Sea Leopard (SS-483), including command of the latter, 1954-56. Ashore he was in the NROTC unit at the University of North Carolina, a student at the Naval War College, and in the submarine readiness section of OpNav. After serving on the staff of ComSubLant, he went through the Navy nuclear power program, then commanded two Polaris submarines, the USS Patrick Henry (SSBN-599) and the USS Casimir Pulaski (SSBN-633). He served next in the Special Projects Office, dealing with Polaris-Poseidon, then was aide to the Under Secretary of the Navy. His first flag billet was as Commander Service Group Three in the Western Pacific during the Vietnam War. Subsequently he served in the Naval Ship Systems Command, as ComSubLant, Deputy CNO (Submarine Warfare), and in two four-star billets: Vice Chief of Naval Operations and Commander in Chief Pacific. In retirement he chaired the Long Commission, which investigated the 1983 bombing of the Marine Barracks in Beirut, Lebanon.