The Paris Commune was a radical socialist and revolutionary government that ruled Paris from 18 March to 28 May 1871. Following the defeat of Emperor Napoleon III in September 1870, the French Second Empire swiftly collapsed. In its stead rose a Third Republic at war with Prussia, who subjected Paris to a brutal four-month siege. A hotbed of working-class radicalism, during this time France's capital was primarily defended not by the regular French Army, but by the often politicized and radical troops of National Guard. In February 1871 Adolphe Thiers, the new chief executive of the French national government, signed an armistice with Prussia that disarmed the Army but not the National Guard.