The ZSU-23-4 "Shilka" system has been - and in many examples continues to be - a much-feared anti-aircraft system for pilots of low-flying aircraft all over the world. The effectiveness of the Shilka at low altitudes is a well documented story as the system has seen considerable action in several major global conflicts. The Shilka was initially reserved mainly for the Soviet Army and her (now former) supported states during the Cold War and went on to be exported heavily to ally nations in Asia, the Middle East, Africa and South America. The Shilka defense system continues to serve in some impressive quantities with several armies around the world despite her 1960s-era origins. At the time of her inception, no anti-aircraft gunnery platform in the NATO inventory could match the lethality that was the ZSU-23-4 Shilka series.
The Shilka came about through a need by the Soviet Army to upgrade its existing self-propelled anti-aircraft gun capabilities. Her primary adversaries of the time were the United States and Great Britain and both were fully capable of fielding top-of-the-line ground attack aircraft including helicopters that would - in the event of all-out war in Europe - be called to limit the usefulness of Soviet armor. At the time, the primary system available to the Red Army was the ZSU-57-2 tracked series mounting a powerful set of 57mm cannons. However, despite this large-caliber armament, the system was inherently limited by its optically aimed tracking system, lack of integrated radar with no provision for engaging targets while "on the move". Onboard ammunition storage capability was also limited to just 300 rounds of 52mm projectiles.
Development on a replacement began in 1957 and continued into 1962. The new design - to become the ZSU-23-4 (otherwise known as the "Shilka" after the Shilka River found in Eastern Russia) - incorporated the tracked chassis of the GM-575 with a flat, rounded turret system mounting 4 x 23mm rapid fire autocannons. A water-cooling system was fitted to keep the guns from overheating and at least 2,000 of 23mm ammunition could be carried aboard. A radar system (the RPK-2 "Tobol") was installed to aid the crew in the tracking and engagement of targets along the rear of the turret roof. The vehicle would be crewed by four personnel made up of a driver, commander, gunner and radar operator with the driver located at the forward portion of the hull and the rest of the crew in the turret. The turret was set at the middle of the hull roof with the engine mounted in a rear compartment. The vehicle utilized six rubber-tired road wheels with a long running set of tracks which gave good cross-country mobility in keeping up with Soviet armored formations. This effectively allowed the weapon to be stationed just about anywhere a tank or similar wheeled vehicle could. The turret allowed for a full 360-degree traversal with extensive elevation that would let the crew engage both low-flying aerial targets as well as ground-based ones. Aerial targets could be engaged at 2.5 miles out while land-based ones at 1.5 miles. The radar itself could pick up targets as far out as 12 miles allowing the crew to be prepared to greet. Armor protection for the crew ranged from over 9mm on the turret to 15mm on the hull. Power was supplied from a V-6R series 6-cylinder, 4-stroke airless-injection water-cooled diesel engine developing 280 horsepower that allowed for speeds up to 50km/h on roads with a range out to 450km. The hull was seated on an individual torsion bar suspensions system with hydraulic shock absorbers fitted to several of the wheel pairings. Production by Mytishchi Engineering Works began in 1964 and continued on to 1982 to which some 6,500 examples were produced all. The ZSU-23-4 formally entered service in 1965 and over 38% of the production total went to serve in 23 countries around the globe.
Once in practice, the Shilka was immediately put to work in replacing the older anti-aircraft defense systems. For a time, she was fielded alongside the outgoing ZSU-57-2 until her own numbers increased. She was used to protect portions of the vast Soviet Union airspace, applying point defense for all types of military value targets, and could create a lethal defensive "umbrella" when coupled with mobile medium- and long-range, anti-aircraft missile-launching systems. Should enemy aircraft evade or try and avoid the missiles, it would have the Shilka to contend with. Even over time, the Shilka system has survived to still be feared by pilots and warplanners alike. Her rapid fire cannons deliver a potent stream of deadly 23mm ammunition and her integrated radar system makes her an accurate gunnery platform with her established ranges. Her tracked nature means that she can be stationed just about anywhere and can also supply support fire when these armored units are on the move. Today, modernized Shilkas have even been upgraded with short-ranged, anti-aircraft missile launchers that increase the system's lethality to an extent - making for a more complete defense piece. These launchers are fitted to the turret sides or roof and work alongside the battery of cannon.
If the Shilka series maintains some inherent limitations it is in her use of the water-cooled cannons, her inherently short-ranged nature and her lack of armor protection from modern portable anti-tank weapons. However, it is a testament to her design that she still maintains something of a battlefield profile even today. From the late 1960s to today, the weapon system has gone on to prove her worth in seeing extensive action during the War of Attrition (1968-1970), the Yom Kippur War (1973), the Vietnam War (1959-1975), the Lebanese Civil War (1975-1990), the Angolan Civil War (1975-1991), the Western Sahara War (1975-1991), the Libyan-Egyptian War (1977), the Ogaden War (1977-1978), the Soviet Invasion of Afghanistan and subsequent war (1979-1988), the Iran-Iraq War (1980-1988), the Lebanon War (1982), the Gulf War (1990-1991), the Georgian-Abkhazian War (1992-1993), the 1st Chechen War (1994-1996), the 2nd Chechen War (1999), the Invasion of Iraq (2003) and the War in South Ossetia (2008).
The ZSU-23-4 has only existed in a few notable variants and many of these have been subtle upgrades and modernizations of previous Shilka generations. The ZSU-23-4VI of 1970 added an improved V-6R-1 series engine while the ZSU-23-4M (known as the "Biryusa") of 1973 fitted a pyrotechnic loading system over the original's pneumatic system while ammunition counts were increased to 4,500 23mm projectiles. The ZSU-23-4MZ fitted a "friend or foe" identification system and became the new Shilka standard for previous models in service ("Shilka" went on to informally represent all further developments of the system despite the "Biryusa" name being used). The Soviet invasion of Afghanistan brought about a revised Shilka in the ZSU-23-4M2 which added a night sighting device and lost the radar installation. In 1999, the ZSU-23-4M4 was unveiled to the public and showcased the latest modern incarnation of the Shilka family line. This particular version fitted a hydrostatic transmission, laser emission sensors for self-defense and electro-optical vision devices for the crew.
Ukraine has since modernized their existing Shilkas and designates them as "Donets". In 1999, the Malyshev Tank Factory out of Kharkov revised the turrets to fit surface-to-air missile defense systems and assembled them onto the chassis of T-80UD Main Battle Tanks. Similarly, the ZSU-23-4MP "Biala" represents a Polish Army upgrade that occurred in 2000. Grim anti-aircraft missiles were added as were digital systems. Some of the largest Shilka operators went on to become Algeria (perhaps up to 300 examples), Egypt (330 examples with more though to be on the way), India (100), Iran (over 100 examples), Iraq (over 200 examples in unknown condition), Libya (250), Syria (400) and Vietnam (100).
Incidentally, the designation of ZSU-23-4 indicated gun caliber ("23") and number of barrels ("2"). The name "Shilka" is derived from the Shilka River in western Russia. The Shilka may also be known under its nickname of "Zeus".