The costs of the Habsburg-Valois wars, waged intermittently through the first half of the sixteenth century, forced the French to increase taxes and borrow heavily. King Francis I’s treaty with the pope (see “France”) gave the French crown a rich supplement of money and offices and also a vested financial interest in Catholicism. Significant numbers of French people, however, were attracted to Calvinism. Calvinism drew converts from among reform-minded members of the Catholic clergy, the industrious middle classes, and artisan groups. Additionally, some French nobles became Calvinist. By the middle of the sixteenth century perhaps one-tenth of the French population had become Huguenots, the name given to French Calvinists.

Both Calvinists and Catholics believed that the others’ books, services, and ministers polluted the community. Preachers communicated these ideas in sermons, triggering religious violence. Armed clashes between Catholic royalist nobles and Calvinist antimonarchical nobles occurred in many parts of France.

Calvinist teachings called the power of sacred images into question, and mobs in many cities destroyed statues, stained-glass windows, and paintings. Catholic mobs responded by defending the sacred images, and crowds on both sides killed their opponents, often in gruesome ways.

A particularly savage Catholic attack on Calvinists took place in Paris on August 24, 1572 , Saint Bartholomew’s Day. The occasion was the marriage of the king’s sister Margaret of Valois to the Protestant Henry of Navarre, which was intended to help reconcile Catholics and Huguenots. Instead Huguenot wedding guests in Paris were massacred, and other Protestants were slaughtered by mobs. Violence spread to the provinces, where thousands were killed. The Saint Bartholomew’s Day massacre led to a civil war that dragged on for fifteen years.

What ultimately saved France was a small group of moderates of both faiths called politiques (POH-lee-teeks) who believed that only the restoration of a strong monarchy could reverse the trend toward collapse. The politiques also favored officially recognizing the Huguenots. The death of the French queen Catherine de’ Medici, followed by the assassination of her son King Henry III, paved the way for the accession of Henry of Navarre, a politique who became Henry IV (r. 1589–1610).

Henry’s willingness to sacrifice religious principles to political necessity saved France. He converted to Catholicism but also, in 1598, issued the Edict of Nantes (nahnt), which granted liberty of conscience (freedom of thought) and liberty of public worship to Huguenots in 150 fortified towns. By helping restore internal peace in France, the reign of Henry IV and the Edict of Nantes paved the way for French kings to claim absolute power in the seventeenth century.