Final answer:
The St. Bartholomew's Day Massacre was a turning point in the French civil war due to political rivalries between Catholics and Protestants, which escalated into a bitter war for religious survival.
Step-by-step explanation:
The St. Bartholomew's Day Massacre, which took place in 1572, was a turning point in the French civil war. The incident was a result of political rivalries between Catholics and Protestants that had been brewing for years. The massacre was triggered by the marriage of a Catholic princess to a Protestant prince, which led to deep divisions and tensions between the two religious groups. The political rivalries between the Catholic and Protestant factions eventually escalated into a bitter war for religious survival.