The ZSU-23-4 "Shilka" is a lightly armored, self-propelled, radar guided anti-aircraft weapon system (SPAAG). ZSU stands for Zenitnaya Samokhodnaya Ustanovka (Russian: Зенитная Самоходная Установка), meaning "anti-aircraft self-propelled mount", 23 stands for the caliber of the armament and 4 stands for the number of gun barrels. It is named after the Russian Shilka River.
The radar-guided ZSU-23-4 "Shilka" SPAAG, with its four 23 mm (0.90") autocannons, was a revolutionary SPAAG, proving to be an extremely effective weapon against enemy attack aircraft and helicopters under every weather and light conditions. The ZSU-23-4 has a very high density, rate and accuracy of fire, as well as the capability for each of the four autocannons to fire its own type of projectiles from separate belts. The appearance of the "Shilka" caused very significant changes in NATO tactics in aircraft use at low altitude over the battlefield.
Despite its present obsolescence as a modern short-range anti-aircraft weapon, the ZSU-23-4 is still deadly for enemy light armoured vehicles, infantry and firing points as an infantry-support vehicle. With its high rate of accurate fire, the "Shilka" can even neutralize tanks by destroying their gun sights, radio antennas, et cetera. "Shilka" (especially late models) have excellent performance and high systems reliability.