Henri III tried to convince Henri de Navarre to convert to Catholicism, as this would remove the cloud over his succession and make for a legitimate transition. Navarre was not ready to do this, as it would have cost him his current base of support. Guise revived the Catholic League with the goal of preventing any heretic from coming the throne. In December of 1584 the Guises signed the Treaty of Joinville on behalf of the League with Phillip II of Spain. Spain poured a huge annual subsidy into the League and Guise pockets for the next decade in an attempt to destabilize the government of France. The royalist, Protestant, and Leaguer forces, all led by men named Henri, were to engage in the bloodiest and longest of the civil wars.
The Duc de Guise and his relations, the Duc de Mayenne in Burgundy, the Duc d'Aumale in Picardy, the Duc d'Elboef in Normandy, the Duc de Mercoeur in Brittany, and the Duke of Lorraine (not a French territory at this time, but bordering it on the northeast) controlled vast amounts of territory (see Map) that were claimed for the League. In addition to this strong noble base, the League had a growing urban following among the middle classes, especially in Paris where the government was eventually in the hands of the League Committee of Sixteen.
Henri III tried to coopt the League as he had done almost 10 years earlier, by putting himself at the head of it. The Treaty of Nemours, signed in 1585, revoked all the previous edicts of pacification: banning the practice of the reformed religion throughout the kingdom, declaring Protestants unable to hold royal office, ordering all garrisoned towns to be evacuated, and requiring all Protestants to abjure their faith within six months or be exiled. Naturally, this lead to war.
The League, under the leadership of Guise, managed to dominate in the north and east. Navarre and Condé entrenched in the south and went looking for foreign aid from the German princes and Queen Elizabeth. In 1587, an army of German mercenaries contributed by Jan Casimir of the Palatinate entered France. Guise took a Leaguer army to deal with them, and Henri III sent the Duc de Joyeuse to cut Navarre off in the southwest. Navarre won the first spectacular Protestant victory at the battle of Coutras, killing Joyeuse and routing his army. Guise, in turn, trounced the Germans and sent them home.
Meanwhile, the people of Paris, under the influence of inflammatory Leaguer preachers and the Committee of Sixteen, were becoming more and more dissatisfied with Henri III and his failure to suppress the Protestants. To be a moderate Catholic was almost as bad as being heretic to the Leaguers, and politique was an epithet of contempt. In May of 1588, a popular uprising where barricades went up the streets of Paris for the first time (the beginning of a venerable French tradition) caused Henri III to flee the city. The Committee of Sixteen took complete control of the government and welcomed the Duc de Guise to the city.
The League pressed for a meeting of the Estates-General, which was held in Blois in the fall. Their proposed heir to the crown was the Cardinal de Bourbon, Navarre's uncle. He was an old man and would have been a puppet figure for the Guises, and there was even a fear that Henri III would be forced to abdicate and that the people might proclaim Guise king. On Christmas Eve in 1588, when Guise was at Blois for the meetings, Henri III invited him to his quarters for some discussion. Perhaps he should have been suspicious of the rows of archers lining the stairs to the king' apartments, and of the 40 gentlemen waiting in the anteroom. When he entered, the doors were bolted and although he struggled heroically, he was cut to pieces, his body burnt, the bones dissolved, and the ashes scattered to the wind. The same fate was visited on his brother, the Cardinal de Guise. This cut the two best heads from the house of Guise, but it still left the younger brother, the Duc de Mayenne, who now became leader of the League.
Henri's triumph over the House of Guise was short-lived. The League presses took over printing revolutionary tracts, exceeding by far in vitriol the earlier anti-royalist works of the Huguenots. The Sorbonne proclaimed that is was just and necessary to depose Henri III, and that any private citizen was morally free to commit regicide. And in fact, one of them eventually did.
The League sent an army against Henri III, and Henri III turned to Navarre for an alliance. The two kings joined forces to reclaim Paris. In July 1589, in the royal camp at St. Cloud, a monk named Jacques Clément begged an audience with the king and put a long knife into his spleen. At first it was thought the king might recover, but the wound festered. On his deathbed, Henri III called for Navarre and named him his heir.
Henri laid siege to Paris in the spring and summer of 1590. Although he reduced it to severe hunger, he made humanitarian gestures like allowing women and children to leave. This is not usually considered militarily wise by a besieger, as it means the only people consuming food in the city are able-bodied combatants. The situation alarmed Philip II of Spain, who ordered the Duke of Parma, perhaps the most able military commander of the age, to divert himself from suppressing the Dutch to relieving the siege. Parma was able to successfully get supplies into the city. The two never met in open combat, but Henri IV was obliged to withdraw.
In 1593, the League held an Estates-General in Paris, to name a candidate for the throne of France. The Spanish proposed the Infanta, the daughter of Philip II by Elizabeth de Valois, the late Henri III's sister, who would be married to a suitable French noble like the young Duc de Guise. This was a shocking departure from the Salic Law (no woman can inherit the throne of France), and Parliament passed a decree that the crown could not go to any foreigner.
At this point, Henri IV made his "perilous leap" and abjured his faith in July 1593, in the church of St. Denis, reputedly with the famous witticism that "Paris is worth a mass." A coronation was arranged for him at Chartres, rather than at the traditional Reims, which was in the hands of the League. This was a blow to the League, as it removed the chief objection of many of the more moderate Catholics to Henri IV. Many people did not trust the conversation, including the Protestants who hoped it was not for real. Still, some of Henri's hardcore Protestant supporters withdrew from him. In the end, he won over enough moderate Catholics to strengthen his position.
Finally, in the spring of 1594, Henri IV entered Paris without firing a shot, and the Spanish garrison marched out. It wasn't over yet, but Henri was now in possession of his capital. He began a vigorous program of winning over the support of moderate Catholics with a combination of charm, force, money, and promises. A great deal of money was spent guaranteeing various nobles pensions and positions in exchange for the support, and a great deal of money was given to the towns in exchange for theirs. Henri himself made the crack that the loyality of the king's "bonnes villes" was "vendu, pas rendu." In the end, Henri considered it a bargain given he alternative costs of war.
Meanwhile, the king of Spain renewed the offensive in the northern territories, hoping to unite with the still rebellious Leaguer lords. Cambrai, Doullens, Calais were all taken in 1595 and 1596. Henri IV besieged La Fere, a Spanish outpost in French territory. In 1597, the Spanish took Amiens. The king fought back quite vigorously. Finally, in 1598, faced with financial problems of their own, the Spanish signed the Treaty of Vervins, which restored the captured towns to France. Of the League leaders, Mayenne capitulated in '96, the young Guise in '95, and Mercoeur at last in '98.
1598 saw the publication of the Edict of Nantes, which granted Huguenots freedom of worship and civil rights for nearly a century, until Henri IV's descendent Louis XIV revoked it in 1685. It is not the end of the Huguenot story in France, but it closes this chapter of the Wars of Religion.