the south. The planners considered that the Châtillon hills to the south of the fort, with their scattered villages, parks and country houses, was out of range. However, a besieger could place his batteries on the wooded and irregular heights without interference from the forts. The long-range rifled guns of 1870, placed on elevated parts of the hills, could easily reach the fort and the city. Structure Fort Issy was typical of the detached forts surrounding Paris, and presumably represented consensus on the ideal fortification. The neighboring forts at Vanves and Montrouge were very similar, but had a square plan. The fort was given a geometrical form in which the bastions included all standard elements, the tennaille, ravelin , redoubt of the covered way and so on. All the faces were the same despite the fact that an attack from the area between the fort and the walls of Paris could only be done by parties of infantry who had infiltrated between the forts. The revetments were very exposed and could easily have been breached by a siege train of the type used by Wellington at the Siege of Ciudad Rodrigo in 1812. At the time of the siege of Paris the fort, including detached outworks, mounted 64 guns. The effective range of the guns was about . The fort was an expensive structure that was very vulnerable to siege batteries, and that exposed long faces to enfilade fire. Siege of Paris The Franco-Prussian War began on 19 July 1870. On 2 September 1870 Napoleon III ordered surrender at the Battle of Sedan. Two days later the mob in Paris declared a Republic, with General Louis-Jules Trochu as provisional head of government. The Siege of Paris began on 18 September 1870 when the Prussians encircled the city, and would last for five months. On 16 December 1870 two companies advanced from Fort Issy to occupy the village of Meudon. They encountered Prussian outposts, lost five casualties and retreated. When they were ready, the Germans had little difficulty in silencing the Paris forts. The Prussian artillery opened its bombardment on 5 January 1871. It continued for 22 days. On 6 January the fire from Fort Issy was temporarily silenced. On 7–8 January the revetments and buildings inside the fort started to be demolished, while the fort's return fire was feeble. The Prussians also directed fire against targets inside Paris. On 11