Carrier was born at Yolet, a village near Aurillac in Upper Auvergne. As the son of a middle classtenant farmer, Jean-Baptiste Carrier and his family survived on income reaped from cultivating the land of a French nobleman. After attending a Jesuit college in Aurillac, he was able to pursue a wide variety of career interests. Carrier worked in a law office in Paris until 1785 when he returned to Aurillac, marrying, joining the national guard and becoming a member of the Jacobin Club. In 1790 he was a country attorney and in 1792 became deputy to the National Convention. He was already known as one of the influential members of the Cordeliers club and of the Jacobin Club. After the subjugation of Flanders he was one of the commissioners nominated in the close of 1792 by the Convention. He voted for the execution of King Louis XVI of France, was one of the first to call for the arrest of the Duke of Orléans, and took a prominent part in the overthrow of the Girondists.
After a mission to Normandy, Carrier was sent, early in October 1793, to Nantes, under orders from the National Convention to suppress the revolt of anti-revolutionists. He established a revolutionary tribunal in Nantes and formed what was called the Legion of Marat, to dispose quickly of the masses of prisoners heaped in the jails. The trial were soon discontinued, and the victims were sent to the guillotine, shot, or disposed of in a more inhumane way. In a twenty-page letter to his fellow republicans, Carrier promised not to leave a single counter-revolutionary or monopolist at large in Nantes. His vigorous action was endorsed by the Committee of Public Safety, and in the following days Carrier put large numbers of prisoners aboard vessels with trap doors for bottoms, and sunk them in the Loire river. These executions, especially of priests and nuns, as well as women and children, known as the Drownings at Nantes, along with his increasing demeanor, gained Carrier a reputation for wanton cruelty. Some alleged that he ordered young male and female prisoners be tied together naked before the drownings, a method which was called a "Republican marriage", but this accusation was later found to be a rumor started by counter-revolutionaries. He was described by Thiers as being "...one of those inferior and violent spirits, who in the excitement of civil wars become monsters of cruelty and extravagance." He also organised the ransack of public storehouses, mills, and bake houses in an effort to find "military" resistance evidenced in hidden weapons, artillery, and gunpowder. Finding little contraband, he nevertheless burned down buildings of every kind in what he identified as "revolting districts."
Trial and conviction
Early in 1794 Carrier was recalled to Paris. A few months later, the Thermidorian reaction led to the fall of Robespierre and the Committee of Public Safety. Carrier's position became dangerously exposed. Prisoners he had brought from Nantes were acquitted and released, and denunciations of Carrier's actions increased. On 3 September 1794 Carrier was arrested. At his trial, in the Salle de la Liberté, Carrier was quick to denounce allegations of inhumanity saying, "I took but little share in the policing of Nantes; I was only there in passing, being first at Rennes and later with the army. My principal task was to watch over and see to the victualling of our troops, and for six months I supplied 200,000 men there without its costing the State a halfpenny. Hence I have little information to offer in the matter. I know little or nothing of the accused." After this statement, a fellow representative sprang to his feet vocally charging Carrier with drownings, wholesale executions, demolitions, thefts, pillaging, laying waste to Nantes, famine and disorder, and with the butchering of women and children. Men from the Marat Company were present during the trial, including Perro-Chaux, Lévêque, Bollogniel, Grandmaison, and Mainguet. All these men were appointed directly and indirectly by Carrier and all were part of the Revolutionary Committee of Nantes. The jury that heard Carrier's case was left dumbfounded as the trial closed and passed a unanimous vote for Carrier's execution, which took place on 16 December 1794. See Comte Fleury, Carrier à Nantes, 1793-1794 ; Alfred Lallié, J. B. Carrier, représentant du Cantal à la Convention 1756-1794 d'après de nouveaux documents.
