Submarine Squadron 4 (also known as SUBRON 4 or CSS-4) is a squadron of submarines based at US Naval Submarine Base New London, Groton, Connecticut. SUBRON 4 has been located in Groton since 9 July 1997. Prior to reactivation in Groton with fast-attack submarines, the squadron, made up of fast-attack submarines, was located in Charleston, South Carolina from 1959–1995. Before Charleston, SUBRON 4 homeport was Pearl Harbor, HI from its founding in 1930 until 1959. Established in 1930 with operations based in Pearl Harbor, HI.