The ZU-23-2 was developed in the late 1950s. It was designed to engage low-flying targets at a range of 2.5 km as well as armoured vehicles at a range of two kilometres (km) and for direct defense of troops and strategic locations against air assault usually conducted by helicopters and low-flying airplanes. In 1955, KBP presented the single-barrel ZU-1 and the twin-barrel ZU-14. While the former was eventually dropped, the ZU-14 was selected and, after some modifications, entered series production.
Additional Information: en.wikipedia.org/wiki/ZSU-23-2