The Royal Australian Navy (RAN) fleet is made up of 47 commissioned warships as of January 2016. The main strength is the eleven frigates of the surface combatant force: eight Anzac class and three Adelaide class. Six Collins-class boats make up the submarine service, although due to the maintenance cycle not all submarines are active at any time. Amphibious warfare assets include two Canberra-class landing helicopter dock ships and the landing ship HMAS Choules. Thirteen Armidale-class patrol boats perform coastal and economic exclusion zone patrols, and four Huon-class vessels are used for minehunting and clearance (another two are commissioned but in reserve since October 2011). Replenishment at sea is provided by two ships, Sirius and Success, while the two Leeuwin-class and four Palum