The primary variant of the aircraft used during the Second World War was the Mk I, which was used in all theatres of operation. Throughout its operational career, the Firefly took on increasingly demanding roles from fighter to anti-submarine warfare stationed mainly with the British Pacific Fleet in the Far East and Pacific theatres. Fireflies carried out attacks on oil refineries and airfields and gained renown when they became the first British-designed and -built aircraft to overfly Tokyo.