The final offensive on Paris by MacMahon's army began early in the morning on Sunday, 21 May. On the front line, soldiers learned from a sympathiser inside the walls that the National Guard had withdrawn from one section of the city wall at Point-du-Jour, and the fortifications were undefended. An army engineer crossed the moat and inspected the empty fortifications, and immediately telegraphed the news to Marshal MacMahon, who was with Thiers at Fort Mont-Valérien. MacMahon immediately gave orders, and two battalions passed through the fortifications without meeting anyone, and occupied the Porte de Saint-Cloud and the Porte de Versailles. By four o'clock in the morning, sixty thousand soldiers had passed into the city and occupied Auteuil and Passy.