High Quality Content by WIKIPEDIA articles! HMS Invincible was a 74-gun third rate ship of the line of the Royal Navy, launched on 9 March 1765 at Deptford.Invincible was built during a period of peace to replace ships worn out in the recently concluded Seven Years` War. The ship went on to serve in the American War of Independence, fighting at the battles of Cape St Vincent in 1780, the Chesapeake in 1781 and St Kitts in 1782.