Churchill, John (1650–1722), 1st duke of Marlborough and general, was born in Devon, son of Sir Winston Churchill (qv), a commissioner of the 1662–3 court of claims, and educated at St Paul's School. Commissioned (1667) as an ensign in the foot guards, in 1672 he served in Tangier and became a captain in Monmouth's regiment of foot, going on to serve in Flanders (1672–7). He became colonel of a regiment of foot (1678) and colonel of the Royal Regiment of Dragoons (1683). Elevated to the peerage as Baron Churchill by James II (qv) in May 1685, he was second-in-command of the royal army during Monmouth's rebellion that year, and was credited with winning the battle of Sedgemoor. On 7 November 1688, while William of Orange (qv) was preparing to invade England, Churchill was promoted by James to lieutenant-general. He deserted to William on 24 November, was created earl of Marlborough (April 1689), and commanded the English contingent at the battle of Walcourt (June). While William was in Ireland in 1690, Marlborough sat on Queen Mary's council. His proposals for the capture of Cork and Kinsale were agreed by William, who was then engaged in the unsuccessful siege of Limerick (August 1690). Marlborough sailed with 5,000 troops and arrived off Cork on 21 September, where by arrangement he linked up with a force of continental troops commanded by the duke of Wurtemberg. Col. Roger MacElligott and his 4,500 men surrendered on 28 September and were taken prisoners of war. On the same day Marlborough sent a cavalry force to Kinsale, on which the garrison abandoned the town and retired into two forts. Marlborough arrived on 2 October and on the next day the smaller James Fort was stormed. Charles Fort surrendered on 14 October, on terms that allowed Sir Edward Scott and his garrison to march to Limerick.
Marlborough left Ireland, never to return, having successfully executed his plans within a month. Alienated by King William's Dutch appointees, he began a treasonable correspondence with Jacobite agents and Princess Anne. He was dismissed from all his positions in January 1692 and was sent to the Tower of London for a month in May on suspicion of treason. In May 1694 he wrote to the exiled King James warning of the English raid on Brest. Marlborough became reconciled to William after the death of Queen Mary in 1695, and commanded the forces in Holland in 1701. On the accession of Queen Anne (1702) he was appointed captain-general of the forces and commenced the first of eleven successful campaigns against the French which included the victories at Blenheim (1704), Ramillies (1706), Oudenarde (1708), and Malplaquet (1709). He was created duke of Marlborough on 14 December 1702, and in 1704 Anne granted him the manor of Woodstock in Oxfordshire and ordered the construction of Blenheim Palace. Amid accusations of corruption and that he had prolonged the war to enrich himself, he was dismissed from all his positions on 31 December 1711. Although a prosecution against him was dropped, he lived in exile from November 1712 to August 1714. In September 1714 he was again made captain-general of the forces. He suffered two paralytic strokes in 1716 and thereafter played little part in public life. He died after a further stroke in 1722 and was buried in Westminster abbey; his body was later removed to Blenheim Palace.
He married (1 October 1678) Sarah, daughter of Richard Jennings of Hertfordshire, and sister of Frances Jennings (who in 1681 married Richard Talbot (qv), duke of Tyrconnell); they had one son and four daughters. His son having predeceased him, his title passed first to his eldest daughter, Henrietta, and then in 1733 to Charles Spencer, his grandson by his second daughter.