I know some of this was said before but here's an overview of the Po-2
The Po-2 was a general purpose utillity biplane (often a crop-duster) that was used as a trainer ("red-flyer) and was also used for transport, and as a military liaison aircraft, due to its STOL capabilities. Later it was also used in the ground-attack role. It had the advantages of cheapness, simplicity and reliabillity, and availabillity. Its also the second most produced aircraft in history with over 40,000 built. It also only had 125 hp for 2,300 lbs loaded or 3,000 lbs max (less tthan .06 hp/lb); considdering that, it did pretty well. The slowness and low stall speed was one of its bigges advantages.
Also: "Although entirely outclassed by contemporary aircraft, the Kukuruznik served extensively on the Eastern Front in World War II, primarily as a liaison, medevac and general supply aircraft. It was especially useful for supplying Soviet partisans behind front line. Its low cost and easy maintenance led to a production run of over 40,000. Manufacturing of the Po-2 in the USSR ceased in 1949, but until 1959 a number were assembled in Aeroflot repair workshops.... After first trials of arming the machine with bombs in 1941, from 1942 it was adapted as a light night ground attack plane.... The material effects of these missions was mostly insignificant, but the psychological effect on German troops was much more noticeable. They typically attacked by complete surprise in the dead of night, denying German troops sleep and keeping them constantly on their guard, contributing yet further to the already exceptionally high stress of combat on the Eastern front. Their usual tactics involved flying only a few meters above the ground, rising for the final approach, cutting off the engine and making a gliding bombing run, leaving the targeted troops with only the eerie whistling of the wind in the wings' bracing-wires as an indication of the impending attack. Luftwaffe fighters found it extremely hard to shoot down the Kukuruznik, because the stall speed of both the Messerschmitt Bf 109 and the Focke-Wulf Fw 190 exceeded the Soviet craft's maximum speed. The U-2 became famous especially as the plane used by the 588th Night Bomber Regiment, composed of all-women pilots and ground crew. The unit became notorious for its daring low-altitude night raids on German rear-area positions, veteran pilots Katya Ryabova and Nadya Popova on one occasion flying 18 such missions in a single night. It is also likely that further demoralization to the enemy occurred due to the pilots being female, and causing significant but mostly intangible losses. As such, they earned the nickname Night Witches (German Nachthexen, Russian Ночные Ведьмы). "
Polikarpov Po-2 - Wikipedia, the free encyclopedia
So it was sort of a bomber (it bombed things) but more of a ground attack, but certainly a combat plane. (though not designed as such)