One of the great bombers of the war, the Ilyushin IL-4 has not unnaturally been overshadowed in Western thinking by the great British and American aircraft, yet well over 5,000 IL-4s were produced between 1937 and 1944, the vast majority in the last three years. The original prototype of this low-wing twin-engine bomber, designated the TsKB-26, flew in 1935, was developed through the TsKB-30, and entered production in 1937 as the DB-3B (DB being a Soviet contraction denoting longrange bomber). Early examples were powered by 571kW M-85 engines, but these were replaced by 716kW M-86s in 1938. Although a tough and relatively simple design, the aircraft suffered from a poor defensive armament of single nose, dorsal and ventral 7.62mm guns, and lost heavily to such aircraft as the Bristol Bulldog, Gloster Gladiator and Fokker D.XXI during the Winter War against Finland in 1939-40. In 1939 a modified version with lengthened nose and more armour (the DB-3F) appeared, and in 1940, in conformity with changed Russian practice, the designation became IL-4 (denoting the designer, Sergei Ilyushin). Soon after the German attack on the USSR opened in 1941 it was decided to withdraw IL-4 production to newly opening plants in Siberia, at the same time replacing a large proportion of the metal structure by less strategically critical wood. IL-4s also entered service with Soviet Naval Aviation, and it was a naval- manned force of these bombers that first raided Berlin from the east on 8 August 1941. Thereafter the IL-4 paid frequent visits to the German capital and other targets in Eastern Europe. In 1944 production ended, although the IL-4 served until the end of the war and afterwards. Apart from increasing the calibre of its guns and giving it a torpedo- carrying ability, the IL-4 remained virtually unchanged between 1941 and 1944.