During 1916, Stabia entered into league competitions for the first time. They were entered into the old Terza Category (today's equivalent is Serie C), Stabia reached the semi-finals before losing 5–1 to Campanian rivals Savoia. Play was halted for World War I, but after it in 1919 the club was refounded thanks largely to Vincenzo Bonifacio. The first game after refounding was a friendly against a team of English sailors who called themselves War Lion, Stabia were victorious, winning the game 6–0. In Castellammare di Stabia a club was founded during August 1919, called "Sport Club War", this was merged with Stabia S.C. by 1920.