The Reign of Terror lasted from September 1793 to July 1794. There were six major factors that made it possible:
1. The external pressure from the Coalition Armies to restore the monarchy.
2. The creation of the Revolutionary Tribunal which became the executioner for the CBS.
3. The establishment of Committee of Public Safety(CBS) for suppressing internal revolts while the National Convention dealt with outside threats.
4. The murder of Jean-Paul Marat and removal of George Danton.
5. Maximilien Robespierre's appointment as a member of CBS.
6. The passing of the Law of Suspects.