After half a century of self-confident but inconclusive pursuit of military glory in Italy, brought to an end by the Treaty of Cateau-Cambrésis in 1559, France was plunged into another period of devastating internal conflict. The Protestant ideas of Luther and Calvin had gained widespread adherence among all classes of society, despite sporadic brutal attempts by François I and Henri II to stamp them out.

When Catherine de Médicis , acting as regent for Henri III, implemented a more tolerant policy, she provoked violent reaction from the ultra-Catholic faction led by the Guise family. Their massacre of a Protestant congregation coming out of church in March 1562 began a civil war of religions that, interspersed with ineffective truces and accords, lasted for the next thirty years.

Well organized and well led by the Prince de Condé and Admiral Coligny, the Huguenots - French Protestants - kept their end up very successfully, until Condé was killed at the battle of Jarnac in 1569. Three years later came one of the blackest events in the memory of French Protestants, even today: the massacre of St Bartholomew's Day . Coligny and three thousand Protestants who had gathered in Paris for the wedding of Marguerite, the king's sister, to the Protestant Henri of Navarre were slaughtered at the instigation of the Guises, and the bloodbath was repeated across France, especially in the south and west where the Protestants were strongest.

In 1584 the king's son died, leaving his brother-in-law, Henri of Navarre , heir to the throne, to the fury of the Guises and their Catholic league, who seized Paris and drove out the king. In retaliation, Henri III murdered the Duc de Guise, and found himself forced into alliance with Henri of Navarre, whom the pope had excommunicated. In 1589 Henri III was himself assassinated, leaving Henri of Navarre to become Henri IV of France. It took another four years of fighting and the abjuration of his faith for the new king to be recognized. "Paris is worth a Mass", he is reputed to have said.

Once on the throne Henri IV set about reconstructing and reconciling the nation. By the Edict of Nantes of 1598 the Huguenots were accorded freedom of conscience, freedom of worship in certain places, the right to attend the same schools and hold the same offices as Catholics, their own courts and the possession of a number of fortresses as a guarantee against renewed attack, the most important being La Rochelle and Montpellier.