John Churchill, 1st Duke of Marlborough (1650-1722), was the oldest surviving son of Sir Winston Churchill, an impoverished country gentleman. After the restoration of Charles II, John's sister, Arabella, became the mistress of the King's brother, James, Duke of York. The family fortunes were made and Churchill's military career launched. In the winter of 1677-78, Churchill married Sarah Jennings, the intimate friend of the future Queen Anne. Ruthlessly changing sides during the Glorious Revolution, he deserted his patron James and joined the army of William of Orange. Marlborough's brilliant generalship in the War of the Spanish Succession destroyed the myth of French military invincibility and won him the adoration of the British people. But Marlborough fell from power when his wife's relationship with Queen Anne ended rancorously and when the peace-loving Tories ousted his wartime supporters, the Whigs.