The Royal Westminster Militia, later the 5th (Reserve) Battalion, Royal Fusiliers, was an auxiliary regiment raised in the City of Westminster in the suburbs of London. Descended from the Westminster Trained Bands, which were on duty during the Armada campaign of 1588 and saw considerable service during the English Civil War, the regiment underwent reorganisation in 1760 as part of the Middlesex Militia. From 1778 until 1918 the regiment served in home and colonial defence in all of Britain's major wars, and supplied thousands of reinforcements to the Royal Fusiliers during World War I. After a shadowy postwar existence the unit was finally disbanded in 1953.