The Polikarpov Po-2 (also U-2, for its initial uchebnyy, 'training', role as a flight instruction aircraft) served as an all-weather multirole Soviet biplane, nicknamed Kukuruznik (Russian: Кукурузник, NATO reporting name "Mule"). The reliable, uncomplicated design of the Po-2 made it an ideal trainer aircraft, as well as doubling as a low-cost ground attack, aerial reconnaissance, psychological warfare and liaison aircraft during war, proving to be one of the most versatile light combat planes.