The siege of Saint-Jean d'Angély (October-3 December 1569) was a Catholic victory that nevertheless cost them so many troops that the Huguenots were able recover the initiative (Third War of Religion).
On 3 October the Royalists (or Catholics) had won a major victory at Moncontour, but instead of pursuing the retreating Huguenot forces they moved south-west, taking a number of Huguenot strongholds, before deciding to besiege St. Jean-d'Angély, 33 miles to the east of La Rochelle. This one was of the last strongholds in Huguenot hands outside La Rochelle, and the Catholic leaders believed that the fall of the one would inevitably lead to the fall of the other.
The Royal army reached Saint-Jean during the second week of October, under the command of Henry, duke of Anjou, the brother of Charles IX. Charles himself appeared on 26 October and summoned the garrison to surrender, but de Piles, the garrison commander replied that he could only surrender the town to the Prince of Navarre, from whom he had received the command.
De Piles commanded a garrison of around 1,500 men, and was massively outnumbered by the Royal army, but despite this the defenders managed to fight off three assaults. Eventually, with ammunition running low, de Piles agreed to a ten day long truce and promised to surrender if no help arrived during that time. Forty horsemen did managed to break through the siege lines during this period, and the siege was resumed, but eventually, on 2 December and with no hope of relief De Piles accepted surrender terms. The garrison were allowed to retreat with their horses, arms and personal effects and religious liberty was to be granted to the townsfolk.
Although the siege ended as a Royal victory, it had a very negative impact on Charles's cause. The Royal army suffered very heavy losses during the siege, some during the fighting, but at least as many from disease. The overall losses were probably around 6,000, although some sources go as high as 10,000 or as low as 2,000. At the same time Admiral Coligny, now the Huguenot leader, was able to recruit a new army in the south of France. Even before the siege ended some members of the King's council had requested peace negotiations, and envoys were sent to La Rochelle, although without success. In 1570 the initiative passed to the Huguenots, and the war was brought to an end by the favourable Peace of St. Germain (8 August 1570).