French Victory at Battle of Rocroi
The Thirty Years' War had dragged on for a quarter century, draining European powers and shifting alliances constantly. Just five days after the death of Louis XIII, Spanish forces under Francisco de Melo laid siege to the border fortress of Rocroi in northern France. The young Duke of Enghien, commanding French troops, marched to relieve the town. On May 19, 1643, French cavalry charges and infantry assaults shattered the vaunted Spanish tercios, long considered Europe's finest infantry. The Spanish army suffered heavy losses, with thousands killed or captured, while French forces secured a decisive win and lifted the siege.
Why it matters: Rocroi ended the myth of Spanish military invincibility that had dominated battlefields for over a century and shifted European power dynamics toward French dominance under the young Louis XIV. The victory boosted French morale during a vulnerable regency period and contributed to the eventual decline of Spanish Habsburg influence in continental affairs.