The military situation in 1792 was deteriorating. Although the Duke of Brunswick, commander-in-chief of the German army, had made his way through Lorraine onto French soil, it was the defeat at Verdun on September 2, 1792 that scared the French deputies. With this Sword of Damocles hanging over the head of Paris, a great many Revolutionaries called for a radical purge of all opposition. Among them was Marat, who exclaimed: "Rise up! Rise up! Let the blood of the traitors flow!" In a similar vein, Danton memorably affirmed, against the Duke of Brunswick and the invaders, "We need audacity, and yet more audacity, and always audacity, and France shall be saved!" *
* Quite an audacious thing to say. He's setting a good example.
At this time, the prisons were filled with thousands of men and women, some hostile to the Revolution such as non-juring priests and former aristocrats, but also common law criminals and lunatics. Fearing that the prisons were a veritable nest of traitors waiting to strike at Paris from within even as Brunswick invaded from without, the revolutionaries made for the prisons and began murdering anyone even remotely suspected of counter-revolutionary sentiment.
Between 1,090 and 1,395 prisoners were killed before the massacres finally ceased. These outbursts of punitive violence had left their mark on the Parisians, although a number of deputies insisted that these actions had been necessary. In the provinces, they engendered disapproval and horror with regard to Paris, but they also spread terror among potential opponents.