Against this backdrop of crisis, the first major religious wars of the period were in France. France was, next to Spain, one of the most powerful kingdoms in Europe. It was the most populous and had large armies. It had a dynamic economy and significant towns and cities. It also had a very weak monarchy under the ruling Valois dynasty, who were kept in check by the powerful nobility. The Valois kings were often no more powerful than their most powerful noblemen, some of the latter of whom had armies as large as that of the king himself, and many Valois kings had little skill for practical politics. For example, the Valois king Henry II ignored affairs of state in favor of hunting and was killed in a tournament (during a joust, a splinter from a broken lance flew in through the eye-slit of his helmet, impaling his eye - he died two weeks later from the subsequent infection), and other members of the dynasty were little more effective.
France was divided between two major factions, led by the fanatically Catholic Guise family and the Huguenot Bourbon family. The former were advised by the Jesuits and supported by the king of Spain, while the latter represented the growing numbers of economically dynamic Huguenots concentrated in the south (they were especially numerous in Navarre, a small independent kingdom between France and Spain that was soon embroiled in the war). As of 1560 fully 10% of the people of France were Huguenots, many of whom represented its dynamic middle class: merchants, lawyers, and prosperous townsfolk. In addition, between one-third and one-half of the lower nobility were Huguenots, so the Huguenots as a group were more powerful than their numbers might initially indicate. Fearing the power of the Huguenots and detesting their faith, the Guises created the Catholic League, an armed militia of Catholics that included armed monks, townsfolk, and soldiers. In 1562 a Guise nobleman sponsored a massacre of Huguenots that sparked decades of war.
From 1562 to 1572 there was on-again, off-again fighting between the Catholic League and Huguenot forces. The French king, Charles X, was a child when the fighting started and the state was thus run by his mother, Catherine de Medici, who tended to vacillate between supporting her fellow Catholics and supporting Protestants who were the enemies of Spain, France’s rival to the south. Despite their own professed Catholicism, neither Charles nor Catherine were fanatical in their religious outlook, much to the frustration of the nobles of the Catholic League.
Hoping to end the conflict, Charles and Catherine invited the Huguenot Prince Henry of Navarre, leader of the Protestant forces, to Paris in 1572 to marry Charles’ sister Margaret. Henry arrived in Paris with some 2,000 Huguenot followers, all of whom had agreed to arrive unarmed. The Duke of Guise led a conspiracy, however, to convince the king that only the death of Henry and his followers would truly end the threat of religious division, and with the king’s approval Catholic forces launched a massacre on St. Bartholomew’s Day, August 24, in which more than 2,000 Protestants were killed. That day, the St. Bartholomew's Day Massacre, would live in infamy in French history as a stark example of religiously-fueled hatred.
The events in Paris, in turn, sparked massacres all over the country with at least 20,000 more deaths (supposedly, the pope was so pleased with the news that he gave 100 gold coins to the messenger who brought it to him). The one important person who survived was the leader of the Huguenot cause, Henry of Navarre, who half-heartedly “converted” to Catholicism to ensure his safety but then escaped to the south and rallied the Huguenot resistance. Charles died in 1574 of an illness, leaving his younger brother Henry as the last male member of his family line available for the throne. After a lull in the fighting, the war resumed in 1576.
In the years that followed, the French Wars of Religion turned into a three-way civil war pitting the Catholic League against the legitimate king of France (both sides were Catholic, but as focused on destroying each other as they were fighting Huguenots) with the Huguenots fighting both in turn. There was almost a macabre humor to the fact that the leaders of the three factions were all named Henry - King Henry III of Valois, Prince Henry IV of Navarre, and the leader of the Catholic League, Henry, Duke of Guise. Further assassinations followed, including those of both the Duke of Guise and the King. The only heir to the throne was Henry of Navarre himself, since he had married into the royal family, so after a climactic battle in 1594 he was declared Henry IV of France. He realized that the country would never accept a Huguenot king, so he famously concluded that “Paris is worth a mass” and converted to Catholicism on the spot.
Henry IV went on to become popular among both Catholics and Protestants for his competence, wit, and pragmatism. In 1598 he issued the Edict of Nantes that officially propagated toleration to the Huguenots, allowing them to build a parallel state within France with walled towns, armies, and an official Huguenots church, but banning them from Paris and participation in the royal government. He was eventually assassinated (after eighteen previous attempts) in 1610 by a Catholic fanatic but, by his death, the pragmatic necessity of tolerance was accepted even by most French Catholics. Ultimately, the “solution” to the French Wars of Religion ended up being political unity instead of religious unity, a conclusion reached out of pure pragmatism rather than any kind of heartfelt toleration of difference.