World War II saw the use of unprecedented airpower and the advent of strategic bombing. This aerial bombardment of heavily populated and industrialized areas caused chaos on the ground, as well as weakening resources for, and strength on, the battlefield. Bombers, therefore, were important tools of war. The Germans used medium-range bombers such as Junkers 88 for long-range reconnaissance, high-speed diving, horizontal bombing and close air support. The Heinkel III was near obsolete but remained in service and the Dornier 217, from mid-1941, was a heavy bomber used on shorter missions. The famous Stuka dive-bomber was a machine of precision, perfect to support Blitzkrieg, and equipped with a terrifying screaming siren. The Russian Petlyakov PE-2 was a fast, agile medium-range bomber used for heavy fighting, reconnaissance missions and night fighting. The long-range Ilyushin IL-4 lacked good defensive capabilities but was used in the bombing of German assets, including Berlin in 1941.