The siege of Paris (30 July-c.5/6 August 1589) saw the combined armies of Henry III and Henry of Navarre besiege Paris, which was held by the Catholic League, but the besieging army fell apart after the assassination of Henry III and the siege soon had to be lifted (Eighth War of Religion).
Henry III had lost control of Paris in May 1588. His rival, Henry of Guise, had entered the city on 9 May, and in response the king had summoned his Swiss troops to the city. This triggered a popular uprising on 12 May (the Day of the Barricades), and Guise and the Catholic League had taken control of the city. The king managed to escape, but he had little support outside the city, and was soon forced to capitulate to the League, signing the Edict of Union (16 July 1588). When the Estates General met in October, Guise pressed his advantage, and continued to gain power. Eventually, on 23 December, the King had him assassinated in the Royal chambers, but this soon backfired. While the King dithered, control of the League passed to Guise’s brother, the duke of Mayenne, Paris turned even further against Henry and declared him deposed and many cities across France sided with the League.
By the spring of 1589 Henry III was ready to come to terms with the Huguenot leader Henry of Navarre. The two kings signed the Treaty of Tours (30 April 1589), in which Henry III agreed to a truce with the Huguenots in return for military assistance. Soon afterwards Navarre’s men helped fight off Mayenne when he attacked Tours, but the two kings were soon able to go onto the offensive and attack Paris.
The two Henrys soon had a powerful army under their command. Henry III hadn’t been entirely idle between the murder of Guise and the treaty of Tours. He had sent envoys to Germany and Switzerland, and they now returned with an army of 10,000 Swiss, 2,000 lansquenets and 1,500 reiters. Henry III advanced from Tours to Etampes and then reached the Seine below Paris. He then besieged and captured Pontoise, cutting the supply lines between Paris and Normandy. The Swiss joined the Royal army after the fall of Pontoise. The combined Royal army was now somewhere between 45,000-48,000 strong, much larger than the League forces defending Paris.
Henry III moved his headquarters to St. Cloud, and besieged Paris from the north, facing St. Honoré, Montmartre and St. Denis. Henry of Navarre was based at Mendon, and besieged Paris from the south, facing St. Germain and St. Marcel. Their plan was to attack the walls on 2 August.
For a few brief weeks Henry III looked to be on top, but this all came to an end outside Paris. A young Franciscan Friar, Jacques Clément, had been boasting about his plans to kill the king for some time, and with the Royal army now outside the city his plans were encouraged. On 31 July he presented himself at Henry III’s headquarters at St. Cloud with a letter claiming that he had important intelligence to give to the King in person. On the morning of 1 August he was admitted to the King’s presence. Henry ordered his attendants to go to the far end of the room, so the message could be given in confidence. Clément handed over a letter, and then stabbed Henry in the abdomen. The king grabbed the knife and used it to strike the assassin, who was then killed by the king’s guards.
At first it looked as if Henry might survive, and messages were sent out with that news, but the wound caused heavy bleeding, and the king died early on 2 August, having ordered his supporters to recognise Henry of Navarre as king.
Henry IV was able to win over the Swiss mercenaries quickly. Two days after coming to the throne he issued the Declaration of St. Cloud, in which he promised to protect the Catholic Church, and in return many of Henry III’s former followers signed a declaration accepting him as King. However those that didn’t accept the new king soon began to weaken the army. The duke of Epernon retired to Normandy, taking 1,200 cavalry and 6,000 infantry with him. Some of Henry’s Huguenot troops left the army after the declaration was issued.
Inside Paris the duke of Mayenne had the Cardinal of Bourbon declared king as Charles X. The Cardinal was actually in Henry’s hands, and so Mayenne became Lieutenant-General of the State and Crown of France.
Henry lifted the siege in early August, with the excuse that he was escorting the body of Henry III to Compiègne to be buried. By this point he only had 1,200 cavalry, 3,000 French infantry and two regiments of Swiss, and Mayenne gave chase with a larger army. However Henry won the first battle of the Ninth War of Religion at Arques (21 September 1589).