By the early 1570s France had already fought three rounds of civil war between its Catholic majority and its Huguenot, French Reformed, minority, and an uneasy peace held long enough for the crown to arrange a marriage meant to bind the two sides together: Margaret of Valois, the Catholic king's sister, to Henry of Navarre, the leading Huguenot nobleman and future Henry IV. The wedding brought much of the Huguenot leadership to Paris in August 1572, a Catholic city where their presence was already resented.
What happened next began as a targeted assassination attempt against the Huguenot military leader Admiral Gaspard de Coligny and spiraled, within days, into a general massacre. Starting in Paris on Saint Bartholomew's feast day, August 24, and spreading to other French cities over the following weeks, Catholic mobs and, in places, royal forces killed an estimated several thousand to as many as ten thousand Huguenots, including much of the nobility gathered for the wedding. The killing shattered any remaining trust between the two communities, drove a new round of warfare, and became, for Protestant Europe for generations afterward, the standing example of Catholic violence against reformed believers, still cited centuries later wherever the period's religious conflicts are discussed.