Thiers had ordered the construction of the fortifications which surrounded Paris, when he was minister of Louis-Philippe. He had designed this enclosure to defend the city against enemies, but had also already calculated at the time that, to put an end to popular insurrections, it was enough to lock the insurgents in the city, then to suppress them. In February 1848, Thiers had vainly proposed this plan to King Louis-Philippe, to crush the Parisian revolution.
On March 17, 1871, Thiers and his government, misjudging the state of mind of the Parisians, sent the troops during the night to seize the cannons of the Montmartre hill. That same day, Thiers took care to arrest Auguste Blanqui (revolutionary insurrectionalist republican nicknamed "L'Enfermé" because he had spent more than half his life in the prisons of kings and the emperor) who was resting at a doctor friend in Bretenoux (Lot). From there, he had him transferred to Brittany, under military surveillance, with orders to shoot in case of escape.
On March 18, in Montmartre, in the morning, the Parisian people opposed the troops that had come to collect the guns, then, quickly, they fraternized with them. A little everywhere in Paris the population attacks the supposed representatives of the government, raises barricades and fraternizes with the troop. Two generals, Claude Martin Lecomte who had given the order to fire on the crowd and Clément Thomas (responsible for the massacres in June 1848), were shot in the rue des Rosiers (part of the present rue du Chevalier-de-La-Barre). This is the start of the uprising. Thiers wins Versailles, about 100,000 Parisians, especially from the chic districts of western Paris and civil servants, follow him there.