The Battle of Two Sisters was an engagement of the Falklands War during the British advance towards the capital, Port Stanley. It took place from 11 to 12 June 1982 and was one of three battles in a Brigade-size operation all on the same night, the other two being the Battle of Mount Longdon and the Battle of Mount Harriet. It was fought mainly between an assaulting British force consisting of Royal Marines of 45 Commando and an Argentine Company drawn from 4th Infantry Regiment (Regimiento de Infantería 4 or RI 4).