The Royal Navy is the principal naval warfare service branch of the British Armed Forces. As of November 2018, there are 75 commissioned ships in the Royal Navy. 20 of the commissioned vessels are major surface combatants (six guided missile destroyers, 13 frigates and one aircraft carrier), and 10 are nuclear-powered submarines (four ballistic missile submarines and six fleet submarines). In addition the Navy possesses two amphibious transport docks, 13 mine countermeasures vessels, 23 patrol vessels, four survey vessels, one icebreaker and two historic warships (Victory and Bristol).