The religious conflicts that plagued France also ravaged the Habsburg-led Holy Roman Empire. The Thirty Years' War eroded the power of the Catholic Habsburgs. Although Cardinal Richelieu, the powerful chief minister of France, had mauled the Protestants, he joined this war on their side in 1636 because it was in the raison d'État (national interest). Imperial Habsburg forces invaded France, ravaged Champagne, and nearly threatened Paris.

Richelieu died in 1642 and was succeeded by Cardinal Mazarin, while Louis XIII died one year later and was succeeded by Louis XIV. France was served by some very efficient commanders such as Louis II de Bourbon (Condé) and Henry de la Tour d'Auvergne (Turenne). The French forces won a decisive victory at Rocroi (1643), and the Spanish army was decimated; the Tercio was broken. The Truce of Ulm (1647) and the Peace of Westphalia (1648) brought an end to the war.