The "Versaillais" went on the attack first. On April 2 they occupied Mont-Valérien, where the Communards had neglected to settle, a considerable advantage, since this position dominated the entire western suburbs of Paris. On March 30, General de Galliffet dislodged the Communards from the Rond-Point de Courbevoie and on April 2 the "Versaillais" seized Courbevoie and Puteaux, while the Communards withdrew towards Neuilly. On April 3 the Commune launched, under the orders of Flourens, Eudes and Duval, a counter-offensive in the direction of Versailles, it ended in failure in Rueil and Châtillon. Gustave Flourens was assassinated by a gendarmerie officer in Rueil, and Duval, without a trial, was shot with his staff on the 4th, on the orders of General Vinoy. On the same day Gustave Cluseret was appointed War Delegate of the Commune. In response to the acts of the Versaillese, the Commune votes, on April 5, the decree of the hostages (3 hostages shot for one Communard executed), which will only be implemented during the Bloody Week at the end of May. For about three weeks, the fighting was sporadic but the bombardments were intensive, in particular on Neuilly, which on the 25th benefited from a suspension of arms to allow the evacuation of the population. This period allowed the Versailles army to strengthen.
On the evening of April 26, the village of Moulineaux was occupied by the "Versaillais", who on the 29th seized Fort Issy (it was reoccupied the next day by the Communards under the command of Rossel). On May 1, Louis Rossel was appointed War Delegate to replace Cluseret, who had been dismissed. On May 4, the Versaillese, certainly aided by treason (which would be the pretext for the arrest of the Dominicans of Arcueil), captured the Moulin-Saquet redoubt, where they committed atrocities. on the 5th, they seized the village of Clamart. On the 8th, the fortified enclosure of Paris was violently bombarded from Grenelle to Passy, while on the 9th, the fort of Issy was taken over by the Versaillese. It was on May 8 that the Thiers government issued an ultimatum to the Parisians who were ordered to capitulate. On May 10, Charles Delescluze replaced Rossel, who had resigned, as War Delegate. On May 13, the Versaillese occupied the fort of Vanves, but were stopped by the artillery of the ramparts of the Commune. On May 17, the cartridge factory on Avenue Rapp exploded following probable sabotage. On May 20, the treachery of Ducatel, a piqueur of the Ponts-et-Chaussées who was in bastion 24, allowed the Versaillese to enter Paris through the Porte de Saint-Cloud. Then begins Bloody Week.