 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on Sunday, 21 May.On the front line, soldiers learned from a sympathiser inside the walls that the National Guard had withdrawn from one section of the city wall at Point-du-Jour, and the fortifications were undefended.An army engineer crossed the moat and inspected the empty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.