The Edict of Union (16 July 1588) saw Henry III of France capitulate to the Catholic League and give in to their demands, having already lost control of Paris to the League (Eighth War of Religion).
By 1588 Paris was dominated by supporters of the Catholic League, but they felt threatened by Henry III’s decision to move some of his Swiss troops close to Paris and to make one of his favourites, the duke of Epernon, governor of Normandy. The Parisian League asked Henry, duke of Guise, to come to the city to protect them. On 9 May, ignoring the king’s orders not to come to the city, Guise entered Paris to a hero’s welcome. Henry III briefly considered assassinating Guise at their first meeting, but lost his nerve. Three days later, on the ‘Day of the Barricades’, he lost his capital as well, after the Parisians built a network of barricades leaving Henry’s Swiss and French guards helpless. Henry showed a brief flash of courage, and escaped from Paris, reaching safety at Chartres, but he then wasted this last chance to regain power, and by July he was ready to come to terms with the League.
On 16 July 1588 Henry III signed the Edict of Union at Rouen. This agreement had ten public and a series of secret articles. In the first he agreed to do everything he could to eliminate heresy, and not to make peace with the heretics or issue any edicts in their favour.
In the second the people of France were ordered to take the same oath.
In the third they were ordered to swear not to recognise any heretic or supporter of heresy as king of France.
In the fourth Henry agreed not to give any military command to a non-Catholic, and that no heretics should be given a judicial or financial office.
In the fifth clause Henry agreed to protect all members of the League against the heretics.
In the sixth clause the population had to swear an agreement of mutual protection.
In the seventh they swore loyalty to the crown.
The eighth clause banned all unions, leagues and associations other than the Catholic League being officially recognised by the Edict of Union.
The ninth declared that anyone who failed to sign the union was guilty of treason.
The tenth clause pardoned the League for all of their acts, and in particular the events of 12-13 May when he had lost control of Paris.
In the secret articles Henry agreed to send two armies against the Huguenots. Guise’s brother the duke of Mayenne was to command the army heading to the Dauphine, while the King was allowed to pick the commander of the army heading to Poitou and Saintonge. The security towns that the League had been granted in the Edict of Nemours of 1585 were to remain in their hands until 1594. They also gained control of a series of important towns such as Orleans and Bourges by being given the authority to select their next governors.
Henry also dismissed his favourite Epernon from government, confirmed the Edict of Nemours and acknowledged Cardinal de Bourbon as his heir-presumptive. Guise was made lieutenant-general of the Kingdom, and given a series of other posts.
Guise didn’t benefit from the Edict of Union for long. In October the Estates-General met at Bloise, and the League dominated them. Henry III decided to take another desperate gamble, and on 23 December he finally had Guise assassinated. This gamble failed, and in April 1589 he was forced to sign the Treaty of Tours, forming an alliance with the Huguenot leader Henry of Navarre. The two Henrys then laid siege to Paris, but on 1 August 1589 Henry III was assassinated, effectively ending the War of the Three Henrys and starting the Ninth War of Religion, fought over the succession of Navarre as Henry IV of France.