Excerpts from Books and Wikipedia
"But, far from stifling Huguenot opposition, the massacre plunged France into another civil war as Huguenots prepared to take up arms against the state." [1001 Days] "The St. Bartholomew's Day massacre (Massacre de la Saint-Barthélemy in French) in 1572 was a targeted group of assassinations, followed by a wave of Roman Catholic mob violence, both directed against the Huguenots (French Calvinist Protestants), during the French Wars of Religion. Traditionally believed to have been instigated by Catherine de' Medici, the mother of King Charles IX, the massacre took place four days after the wedding of the king's sister Margaret to the Protestant Henry III of Navarre (the future Henry IV of France). This marriage was an occasion for which many of the most wealthy and prominent Huguenots had gathered in largely Catholic Paris." [Wikipedia] "The massacre of French Huguenots on August 24, 1572 was the worst atrocity of the French wars of religion. One of the Huguenot leaders, Admiral Gaspard de Coligny, had persuaded the king, Charles IX to intervene to help the Dutch in their struggle against their Spanish overlords. Catherine de Medici . . . feared a Franco Spanish war . . ."