The ZU-23-2, also known as ZU-23, is a Soviet towed 23 mm anti-aircraft twin-barreled autocannon. ZU stands for Zenitnaya Ustanovka. The GRAU index is 2A13. 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 and for direct defence of troops and strategic locations against air assault usually conducted by helicopters and low-flying airplanes.