At the start of the English Civil War in 1642, Ludlow engaged as a volunteer in the life guard of Lord Essex. His first battle was at Worcester on 23 September 1642, and his next at Edgehill on 23 October 1642. In 1643 he returned to Wiltshire and became captain of a troop of horse for Sir Edward Hungerford's regiment. Hungerford made him governor of Wardour Castle in 1643, but he had to surrender to the Royalists after a tenacious three-month defence on 18 March 1644.