After his father's final exile, Berwick served in the French army under Marshal Luxemburg. He fought at the battles of Steenkerque. Luxemburg fell into William's trap set against superior numbers, but reinforcements failed the English, and the French rallied to send the Maison Militaire du Roi infantry downhill. Berwick was in the charge of the division that broke the English lines. They were driven from the field with heavy losses. Berwick was one of Luxemburg's principal officers, and in 1694 commanded the centre of a large French army. After several forced marches to entrap William, they crossed the Meuse again before stopping them near Neerwinden. Berwick struggled against the Foot Guards, who forced his men to retreat in the Landen. He was taken prisoner by his cousin, Charles Churchill, and ransomed for 30,000 florins; and later was exchanged for a wounded Duke of Ormonde. The Irish peer was accused of allowing himself to fall into enemy hands. The scandal swept Whitehall Palace causing angry questions in Parliament.