The Third War of Religion (1568-70) was significantly longer than the first two wars, and although it was marked by two major Catholic victories, at Jarnac and Moncontour, ended as a third Huguenot victory.
The Second War of Religion came to an end early in 1568. Although the Huguenots had been defeated outside Paris (battle of St. Denis, 10 November 1567), they had gone on to besiege Chartres (24 February-March 1568). The peace party at court had prevailed, and the Edict of Longjumeau of 23 March 1568, which gave the Huguenots a limited right to worship, had ended the war.
Even as the peace was being negotiated some of the Huguenot leaders, including Admiral Coligny, had warned that the court was not genuinely interested in peace, and was simply negotiating in order to save Chartres. Their chosen negotiators were almost certainly genuinely interested in peace, but equally there were factions at court who were just as opposed to the treaty as Coligny. The role of Catherine de Medici, the Queen Mother and probably the most important figure in the court of Charles IX is less clear, but the events of the autumn suggest that she was either insincere in the spring or quickly changed her mind.,
The terms of the Edict of Longjumeau were very slow to come into force. The individual Parliaments had to ratify the edict, but dragged their feet. The Parliament of Toulouse only acted after receiving four official orders to do so from Charles. When the Parliament of Rouen ratified the Edict in early April it triggered a riot. The peace certainly improved the Court's military position. While the Huguenot armies quickly disbanded, most of the Royal forces were retained. Charles then began to attack the terms of the treaty itself, deciding to exclude Auvergne, Anjou, Alençon and any lands held by the Bourbon princes. Away from the court a wave of murders swept France, and more Huguenots were killed during the short peace than during the Second War of Religion.
The main Huguenot leaders, Condé and Coligny, were sufficiently concerned about their own safety to move away from Paris. Condé moved to Noyers in Burgundy, where he held land through his wife, while Coligny moved to nearby Tanlay.
By the early autumn the strongly Catholic and anti-peace faction, led by the Guise family (especially Charles, Cardinal of Lorraine), was firmly in power at the court. A plot was hatched to capture the key Huguenot leaders and then suppress the Huguenots. A strong force under Gaspard de Tavannes was sent to arrest Condé and Coligny at Noyers. News of this plot reached Condé just in time, and on 23 August he and Coligny left the chateau, slipped out of the trap and headed for the Huguenot stronghold at La Rochelle. Conde, Coligny and an increasingly number of refugees arrived at La Rochelle on 18 September.
The flight of the Huguenot leaders from Burgundy to La Rochelle marks the start of the Third War of Religion. Condé sent out messages to his fellow protestant leaders as he moved, and soon they began to appear at La Rochelle. The Queen of Navarre arrived on 29 September, bringing with her the young Henry of Havarre (the future Henry IV).
Coligny's brother François d'Andelot arrived with troops from Normandy and Brittany, after slipped past a Royal army. The combined Huguenot army was now strong enough to go onto the offensive, and they captured a number of key cities in Poitou, making La Rochelle more secure. They were further reinforced by an army that had marched up from the south east of France, suffering a minor defeat at Mensignac (25 October 1568) on the way.
On the Royal side any pretence of toleration was soon abandoned. In late September a new edict was issued banning Protestant worship. All ministers were to leave France within fifteen days, and all Protestants were stripped of any official office.
The two sides now controlled significant armies. Condé had somewhere between 19,500 and 30,000 men, while the Royal army, under the official command of Henry of Anjou (The future Henry III) was probably about the same size. Real control of the Royal army was held by Gaspard de Tavannes. Some inconclusive campaigning followed in the late autumn of 1568 before both sides withdrew into winter quarters, with the Royal army at Saumur, Chinon and Poiters and the Huguenots further west at Partenay and Niort.
In the spring of 1569 Condé and Coligny left La Rochelle and moved south in an attempt to join up with the Army of the Viscounts, moving up from the south. The Royal army, under Henry of Anjou (the future Henry III) and Gaspard de Tavannes also moved south, and the two sides clashed at Jarnac on 13 March 1569. Condé was killed in the battle, but most of the Huguenot forces escaped intact. Anjou attempted and failed to capture Cognac, and the battle had few long term results.
The Huguenots now received reinforcements from Germany, led by Wolfgang, duke of Zweibrucken. A Royal army sent to block him failed, and the Germans and Huguenots were united at St. Yrieix in June. By this point Zweibrucken was dead (of natural causes), and Coligny took command of the combined army. The Huguenots won a minor victory at La Roche-Abeille on 25 June and then moved on to besiege Poitiers (July-September).
This siege was a disaster for the Huguenots. The defenders included the young Henry, duke of Guise, who began to earn a reputation for bravery. Coligny attempted to attack the city across a river, and when he did make an assault on an exposed suburb it was defeated.
After the battle of La Roche-Abeille the Royal commanders had decided to temporarily disband most of their army in the hope that the Huguenot army would wither away without a clear opponent. This had not happened, and so Anjou (and Tavannes) regrouped and moved to threaten Châtellerault. This forced Coligny to lift the siege of Poitiers, which came to an end on 7 September. The siege cost the Huguenots at least 2,000 men, but worse was to come.
As Coligny moved north, Anjou retreated to Chinon. The armies then spent much of September separated by a short distance. Coligny didn’t want to risk a battle, but most of his army wanted to fight, as did Anjou. Towards the end of September the Royal army finally made its move, crossing the Vienne and moving south-west in an attempt to cut the Huguenots off from their bases in the west. Coligny managed to march across the front of the Royal army, and reached apparent safety at Moncontour on the Dive, but on the night of 2-3 October the Royal army marched around the southern end of the river and forced the Huguenots to fight on the plains to the south-west of Moncontour. The resulting battle was a clear Royal victory, but Anjou failed to take advantage of his success and instead moved to besiege Saint-Jean d'Angély, a siege that lasted into December, saw the Royal army suffer heavy losses and gave Coligny the time he needed to build a new army in the south of France.
While these events were going on the west, a separate campaign was being fought in the south west, where a Royal army under Terride had conquered most of the kingdom of Navarre, then a small independent state in the south-west of modern France, ruled by Henry of Navarre, the future Henry IV. Terride had been aided by a pro-French revolt in Bearn, and the Queen's lieutenant had been forced to take refuge in Navarreins. The resulting siege of Navarreins lasted from 27 April until early August, and only ended when a Huguenot army led by Count Gabriel of Montgomery appeared on the scene. Montgomery had been sent from Poiters by the Queen with very few troops. He then joined up with the Army of the Viscounts, a small force that has stayed loyal to the Queen, lifted the siege, and then moved on to defeat Terride again at Orthez in mid-August. Terride was killed in the aftermath of the Huguenot victory, and their control of the south-west was restored.
By the start of 1570 the Huguenots had a strong position in the south-west of France, but Coligny believed that the only way to force the Court into serious peace talks would be to advance back into the north. His plan was to cross over to the Mediterranean coast, then advance up the Rhone. Toulouse resisted a month-long siege (22 January-20 February 1570), but after this the Protestants were more succesful. Coligny defeated a Royal army at Arnay-le-Duc in June 1569, and threatened Paris.
In the aftermath of Arnay-le-Duc Charles IX decided to make peace. The resulting Peace of St. Germain was similar to the treaties that had ended the First and Second Wars of Religion, giving the Huguenots the right to worship in a limited number of locations, but it also gave them four 'security towns', which they were to hold for two years. The peace lasted for a similar period, before being shattered by the St. Bartholomew's Eve Massacre of August 1572, which triggered the Fourth War of Religion.