The U-2, or Po-2, was a multi-role biplane, created by Nikolay Polikarpov in 1928. The U-2 was designed as a primary civilian trainer and was forgiving and easy to fly. Its inaugural flight took place on 7th January 1928, with M. M. Gromov at the controls. As designed, the U-2 was a conventional biplane with an air-cooled 100-HP M-11 engine.
The aircraft was widely used in agriculture, transport and other roles. Staff plane and ambulance variants also existed, as well as reconnaissance, passenger, floatplane and many other versions.By 1932 a new military trainer variant, U-2VS was designed. It could carry six 8-kg dummy bombs on underwing pylons and had a gunner turret in the rear seat.
After the German invasion of the Soviet Union in 1941, many existing U-2s were converted to light night bombers. Modifications were made by both the Polikarpov Design Bureau, directly at the factories, and even in the field, by mechanics at front-line squadrons. As a result, the number of operational variants was high. The plane could carry from 100 to 350 kg of bombs. By 1943, the number of frontline Po-2 regiments reached its peak of up to 70 night bomber regiments. After Nikolay Polikarpov died in 1944, the aircraft was redesignated Po-2 in his memory.
The aircraft remained in serial production until 1953, with over 33,000 built.