It was a mass murder in 1572, which began on August 24, the Roman Catholic feast day of St. Bartholomew. The slaughter, which eventually claimed an estimated 70,000 lives, was part of decades of civil wars between Roman Catholics and Protestants (Huguenots) in France.

The Protestant Reformation had begun in 1517, and it spread through Europe over the following decades. By the 1560s as many as one-third of the French people were Protestants. The growth of a reformed Christian faith threatened the Roman Catholic Church and eroded its power, both religious and political. In 1560 Charles IX (1550–1574), a Roman Catholic, rose to power in France. But since he was just 10 years old at the time, the country was ruled by a regent, his mother, Catherine de Medicis (1519–1589). Catherine was a descendant of the powerful Medici family of Florence and, as the wife of King Henry II (1519–1559), the queen of France. Even after Charles IX reached the age of majority, she continued to dominate him.

By 1572 Catherine feared the growing influence that another person, Admiral Gaspard de Coligny (1519–1572), had on her son, the king. Coligny was a leader of the Huguenots, the French Protestants, and, in fact, he did hold sway over Charles IX. To remove this threat, Catherine authorized a plot by Roman Catholic nobles to assassinate Coligny. On August 18, Catherine’s daughter, Margaret of Valois (1553–1615), was married to Henry of Navarre (1553–1610), a Huguenot. The royal event brought many Huguenot nobles to Paris. On August 22, an attempt was made on Coligny’s life, but he survived. Catherine feared that an investigation into the attack on Coligny would reveal her role in it. She therefore gave approval to a wider plan to exterminate Huguenots, and she convinced her son, Charles IX, to order it. According to French statesman and historian Jacques-Auguste de Thou (1553–1617), the order stated that “it was the will of the king that, according to God’s will, they should take vengeance on the band of rebels [the Huguenots] while they had the beasts in the toils.”

The massacre began with the toll of a palace bell on August 24. Those who carried out the killings on the Huguenot leaders identified themselves with white armbands and a white cross on their hats. Coligny was among the first victims, but Protestants throughout Paris were targeted. As citizens became involved in the mayhem, several thousand perished in the city, causing the waters of the River Seine to run red. Throughout the provinces over the next several weeks, thousands more died, the victims of mob attacks on Protestants. News of the attacks was greeted with approval by Roman Catholic leaders; Protestants throughout Europe were horrified. The plot carried out on St. Bartholomew’s Day had launched a mass extermination, fueling the hatred between Catholics and Protestants.