The siege of Orleans (4 February-March 1563) was the last major military action of the First War of Religion, and ended after the assassination of Duke François of Guise, the last major Catholic leader in the field.
Guise had become the sole Catholic leader as a result of the battle of Dreux (19 December 1562). Although this had been a Catholic victory two of their leaders had been lost - Anne, duke of Montmorency having been captured and Marshal Saint-André captured and then murdered. On the Huguenot side the Prince of Condé had also been captured, leaving Admiral Coligny as the main Protestant commander.
In the aftermath of the battle Coligny retreated to the main Huguenot stronghold at Orleans, before on 1 February leaving the city with his German cavalry. François d'Andelot was left to command the defence of the city.
The duke of Guise reached Orleans on 4 February, and the siege began on the following day. On 6 February the Catholics had their first major success. The main city of Orleans, on the north bank of the Loire, was connected by a bridge to the suburb of Portereau on the southern bank. The suburb had weaker defences than the main city, but its walls were protected by two bastions, one garrisoned by Gascon infantry and the other by German infantry. Guise sent his main army to make a feint against the bastion held by the Gascons, while a small force captured the other bastion. The suburb was quickly in Catholic hands, and the defenders only just prevented them from crossing the bridge into he main part of the city.
The siege was noteworthy for one of the first uses of brass shells in warfare. The English Ambassador, Sir Thomas Smith, who was observing the siege with the Royal court at Blois, recorded his impressions in a letter to the Privy Council -
' I have learned this day, the fifteenth instant, of the Spaniards, that they of Orleans shoot brass which is hollow, and so devised within that when it falls it opens and breaks into many pieces with a great fire, and hurts and kills all who are around it. Which is a new device and very terrible, for it pierces the house first, and breaks at the last rebound. Every man in Portereau is fain to run away, they cannot tell whither, when they see where the shot falls'.
The nature of the siege, and of the entire war, changed dramatically on 18 February. The Royal siege works had progressed to the point where Guise was planning to launch an attack on the city on 19 February, and on the evening of the 18th he visited the works to inspect them. On his way back from this inspection he was shot and mortally wounded by a man on horseback. The assassin initially made his escape, but was later arrested when he became lost in the dark. The assassin, Jean Poltrot, lord of Mérey in Angoumois, was motivated by a desire to get revenge for Guise's persecution of the Huguenots. He was eventually executed for his crime, but outlived Guise, who died on 24 February 1563.
The death of Guise left Catherine de Medici free to begin peace negotiations. On 8 March the prince of Condé and the duke of Montmorency were both released, and a peace began on the same day. The basis of the Edict of Amboise was agreed on 12 March, and the treaty was signed by Condé on 18 March. The Huguenots won a limited amount of legal toleration, and four years of peace followed before the outbreak of the Second War of Religion.