Fort d'Issy was one of the fortifications of the city of Paris, France, built between 1841 and 1845.It was one of six forts built to the south of the main wall around the city.The fort was placed too close to the city to be effective, and had a poor design that did not take into account recent experience of siege warfare. It was quickly silenced during the Franco-Prussian War of 1870–71.After the armistice of February 1871 the fort was defended by National Guards of the Paris Commune against the French regular army in April–May 1871.The defense was irresolute and the fort was soon occupied.Today the site of the fort is an "eco-district", an ecologically friendly residential area.