Following the second French Revolution and the Battle of Tuileries, there was a period of great anxiety in France. The attempt by the Duke of Brunswick to orchestrate a foreign backed invasion of France, sponsored by the French Monarchy had raised the stakes to an extreme level and the French army was without a leading general following the defection of theMarquis de Lafayette to the Austrians.
Counter revolutions occurred in in Brittany and on the 2nd September, the Prussians captured Verdun. Verdun represented the last major town between the Prussians and Paris, thus prompting terror of an invasion that would seek revenge for the revolution. Tales that Royalist soldiers would be released and criminals incorporated into the invading army lead to general alarm throughout France. Although most of the Founding Fathers (notably John Adams, Alexander Hamilton, and George Washington) were sickened by the atrocities conducted by the September Massacres, others, such as Thomas Jefferson and Thomas Paine, gave token support, with Jefferson in particular writing the Adam and Eve letter where he coined the phrase that the tree of liberty has to be watered occasionally with the blood of patriots and tyrants.
On the afternoon of the second, a coach of suspected royalists in Paris was being transported towards prison and surrounded. A fracas ensued and the defenders were slaughtered. This was the beginning of the massacres. Rumours of a plot to free the criminals in the overcrowded Parisian jails and the shortage of troops and weapons in the capital itself created a situation of high tension. Jean-Paul Marat called for the execution of the conspirators and a mob of sans-culottes arose to follow his lead. This was the beginning of the Reign of Terror under Maximilien de Robespierre and in the five days following 2 September between 1100 and 1400 of 2600 prisoners were killed.
The left-wing French philosopher Michel Foucault, during a debate with Maoists, advocated for the concept of popular justice over any use of courts, even Socialist people's courts, and cited the September Massacres as an example of popular justice being enacted.