Maximilien Robespierre was known as the "incorruptible" because he refused to take bribes or to profit from the revolution. Robespierre believed that he had to root out all opposition to the revolution. Terror was his method and the motto of the Jacobins: "Let terror be the order of the day!" Terror, he claimed, would allow virtue to flourish.
In September 1793, the Committee of Public Safety introduced the Law of Suspects. Under it, people had only to be suspected of being a traitor -- or of not wholeheartedly agreeing with the revolution -- to be brought to trial and condemned. They were brought by the thousands to the guillotine. On October 1, the prisons held 2,400 "suspects" awaiting trial and execution. By late December, they held 4,500. By the end of the Terror, people were being tried in groups of up to 50 at a time and sent to execution. The final death toll: 40,000 Frenchmen and women were guillotined or shot.
Robespierre turned on his fellow Jocobins and this became his undoing. The Jocobins had grown tired of the blood and the deputies began shouting "Down with the tyrant!" and "Long live the Republic!" He was soon taken to his execution by guillotine.
Source: History and Geography Pearson Learning Core Knowledge