 Bitter fighting followed, as MacMahon's army worked their way systematically forward to the walls of Paris.On 20 May, MacMahon's artillery batteries at Montretout, Mont-Valerian, Boulogne, Issy, and Vanves opened fire on the western neighbourhoods of the city—Auteuil, Passy, and the Trocadero—with shells falling close to l'Étoile.Dombrowski reported that the soldiers he had sent to defend the ramparts of the city between Point du Jour and Porte d'Auteuil had retreated to the city; he had only 4,000 soldiers left at la Muette, 2,000 at Neuilly, and 200 at Asnieres and Saint Ouen.