The Polikarpov Po-2/U-2 was a light bomber that was used by the Soviet Union during WWII.
The U-2 was powered by a Shvetsov M-11 engine that was capable of propelling it at speeds of up to 150 kilometers per hour. However, the stalling speed of the U-2 was only 64 kilometers per hour. This meant that the U-2 was extremely hard to intercept because advanced fighters such as the Bf 109 and Fw 190 would stall before they could get a shot upon the aircraft. The total weight of the U-2 was around 635 kilograms unloaded while the total length was around 8.1 meters. The service ceiling was only 4,000 meters with rate of climb only being 166 meters per minute.
The operational range of the aircraft was 630 kilometers. The first U-2 model was unarmed, though the later ground attack models could either be equipped with four rockets, six 50 kilogram bombs, and a 7.62mm machine gun mounted in the rear gunner position. The U-2 was of a wooden construction covered in canvas. The aeilrons and rudder were connected by exterior cables running along the length of the aircraft.
What made the U-2 so effective in combat was that it was extremely cheap to produce. It was a simplistic aircraft with very few advanced parts. This also aided maintenance in the field. Being produced at a rapid rate, the U-2 could be replaced easily when aircraft were lost in combat.
The U-2, being the most produced biplane in the world, naturally had many different variants of itself designed to keep up with demands. The first of these military variants was the U-2LSh which was the standard ground attack model used during the war. Other specialty variants were also built, such as the U-2GN "Voice from the Sky", a propaganda aircraft with loudspeakers to demoralize enemy combatants. Next was the U-2S, a model fitted with stretchers to evacuate wounded personnel. The U-2ShS was a staff aircraft used to move critical personnel from place to place. The U-2VS was a training model and the U-2LNB was the definitive night harassment bomber. The U-2NAK was used as an artillery spotter. The difference between the Po-2 and the U-2 was that the latter was renamed to the Po-2 in 1944 following a request to honor the original designer of the aircraft.
The U-2 was initially developed in 1926 as a general purpose civilian aircraft by Nikolai Polikarpov. Its first flight took place in 1927 but was rejected and flew once more in 1928 with more satisfactory results. Production then began with thousands of U-2s being produced over the years in the civilian market. However, there was some interest by the Soviet military and several examples were purchased and put into service in various roles.
By the time the U-2 was really needed in 1941, around 13,000 examples had been created and many were already in service with Red Army units. The most notable use of the U-2 in combat was with the 588th Night Bomber Regiment, also known as Nachthexen (the "Night Witches"). This group of female Soviet aviators conducted air raids against German units under the cover of darkness, harassing motor vehicles and air fields. They utilized their slow speed to their advantage to avoid interception. In all its roles, the U-2 continued to be used until the end of the war. In total, around 33,000 models had been produced during the war.