Following acceptance trials, a visit to Havana, Cuba from 14–19 January 1920, and subsequent operations along the Gulf of Mexico and New England coasts, "S-4" departed New London, Connecticut on 18 November to rendezvous off New Hampshire with her assigned unit — Submarine Divisions 12 (SubDiv 12) — and SubDiv 18. The two divisions were about to embark on a historic voyage which, at that time, was to be the longest cruise undertaken by American submarines. Assigned to Submarine Flotilla 3 of the Asiatic Fleet at Cavite in the Philippine Islands, they sailed via the Panama Canal and Pearl Harbor and arrived at Cavite on 1 December 1921.