Operation Retribution was the April 1941 German bombing of Belgrade, the capital of the Kingdom of Yugoslavia. The bombing deliberately targeted the killing of civilians as punishment and resulted in 17,000 civilian deaths. It occurred in the first days of the World War II German-led Axis invasion of Yugoslavia. The operation commenced on 6 April and concluded on 7 or 8 April, resulting in the paralysis of Yugoslav civilian and military command and control, widespread destruction in the centre of the city and many civilian casualties. Following the Yugoslav capitulation, "Luftwaffe" engineers conducted a bomb damage assessment in Belgrade. The report stated that of bombs were dropped, with 10 to 14 percent being incendiaries. It listed all the targets of the bombing, which included: the royal palace, the war ministry, military headquarters, the central post office, the telegraph office, passenger and goods railway stations, power stations and barracks. It also mentioned that seven aerial mines were dropped and that areas in the centre and northwest of the city had been destroyed, comprising 20 to 25 percent of its total area. Some aspects of the bombing remain unexplained, particularly the use of the aerial mines. In contrast, Pavlowitch states that almost 50 percent of housing in Belgrade was destroyed. After the invasion, the Germans forced between 3,500 and 4,000 Jews to collect rubble that was caused by the bombing.