The Jacobins served as the primary promoters of republicanism during the French Revolution, and they passed various reforms to promote equality and personal freedom during their brief control of France. However, they ushered in the Reign of Terror, a period of time when the Jacobins sought out and executed anyone whose political beliefs differed even slightly from their own.
The Jacobins were formally known as the Society of the Friends of the Constitution. The club was originally founded by Breton representatives to the Estates General of 1789, but it eventually expanded beyond Brittany until there were chapter houses throughout France. The name Jacobin comes the fact that they met in Paris in a Dominican monastery; the monks of this order were also called Jacobins because their first house was on the Rue St. Jacques.
The Society of the Friends of the Constitution did not call for the end of the monarchy, but they did manage to become a major force in the National Convention. Eventually they staged a coup, and in 1793, the leader of the Jacobins, Maximilien Robespierre, came to dominate the new French Republic. While he initially passed a number of laws to help the common people of France, such as fixing prices to battle inflation, he soon began persecuting anyone with beliefs he deemed to be counterrevolutionary. He initially targeted supporters of the monarchy, merchants, and other dissenters, but soon even other Jacobins who disagreed only slightly with Robespierre were executed by guillotine.
Eventually, the other Jacobins turned on Robespierre, who was then executed in turn. However, without their organization binding them together, the Jacobins soon lost power to members of the bourgeoisie. Many Jacobin reforms were soon undone, but their strong support for liberty and equality continued to influence later political groups in the French Republic.