The Siege of Derry (Irish: Léigear Dhoire) involved a pre-emptive lockdown of the gates of Derry in December 1688 and a violent defensive action lasting from 18 April to 28 July 1689, during the Williamite War in Ireland. The city, a Williamite stronghold, was besieged by a Jacobite army until it was relieved by Royal Navy ships. The siege is commemorated yearly in August by the Apprentice Boys of Derry.