In 1572 four inter-related incidents occurred after the royal wedding of Maguerite of Valois to Henry of Navarre. On 22nd August a Catholic named Maurevert attempted to assassinate Admiral Coligny, leader of the Huguenots in Paris. In the early hours of the morning of 24th August, St. Bartholomew's Day, several dozen Huguenot leaders were murdered in Paris. Beginning on 24 August, and lasting three days, there was a wave of popular killings of Huguenots by the Paris mob. From August to October massacres of Huguenots took place in other towns, such as Toulouse, Bordeaux, Lyon, Bourges, Rouen, and Orléans. Estimates of the numbers of those murdered range as high as 100,000. Historians generally agree on the figure of 70,000. Contemporary accounts report bodies in the rivers for months afterwards. It was not the first such pogrom of the Wars of Religion, nor would it be the last.
After the third war in 1570, there was a possibility of peace, the House of Guise had 'fallen from favour at the court'. They had been replaced by Catholics who were more willing to find a solution to the crisis. The Huguenots were in a strong military position as a result of the Edict of Saint-Germain. They controlled the fortified towns of La Rochelle, La Charité, Cognac, and Montauban. Catherine de Medici had hoped the marriage alliances of her children would support her move for peace, the marriage between Elizabeth I and her son the Duke of Anjou (Henry III). By 1572 hopes of peace were collapsing. In 1571 the Catholic fleet under Don John of Austria defeated the Turks at the Battle of Lepanto. This confirmed to the Huguenots that Catholicism may resurge across Western Europe led by Philip II. In April 1572, 'Sea Beggars' took control of Den Briel thus taking control of Holland. This meant that there was pressure within France to intervene on behalf of the rebels in the Netherlands to prevent a Spanish intervention in France. Admiral Gaspard de Coligny was the leader of the Huguenots and was the main supporter of this intervention. There was then the possibility of another civil war or a major war against Spain, which was at that time western Europe's greatest Catholic power. Relations between the Huguenots and the Catholics had deteriorated by 1572, and in Rouen on a Sunday in March 1571 forty Huguenots had been killed because they refused to kneel in front of the host during a Catholic procession.
The Guise faction had fallen from favor in the court, and Coligny was readmitted into the king's council in September 1571. The Guises hated Coligny for two reasons: he was the leader of the Huguenots, and he was implicated in the assassination of Francis, Duke of Guise, in February 1563.
Background to the massacres
The story was fictionalized by Alexandre Dumas in La Reine Margot, an 1845 novel that is accurate as far as the historical facts go but fills in with romance and adventure between them. That novel was translated into English as Queen Margot, which was made into a successful film in 1994.