The ZU (Зенитная Установка/Zenitnaya Ustanovka-antiaircraft installation)-23-2 is a Soviet-Cold War era twin gunned towed Air Defense Artillery (ADA) system using 23mm-by-152mm rounds.
The ZU-23-2 is also known as 2A13.
The ZU-23-2 was developed in the late 1950s from a prototype known as ZU-14. It entered service with the Soviet Union in 1960, and is still in production in Russia (upgraded to launch missiles and be remotely controlled), including licensed production in several former Warsaw Pact countries which are now part of NATO. Even Israel has helped Viet Nam develop its own version of the ZU-23-2, known as the 23-2M.
Sometime during the Cold War, a Yugoslavian(?) ZU-23-2.
Interestingly, during the Cold War most books about Soviet weaponry, published in the NATO West, never mention the ZU-23-2. Yet, today the ZU-23-2 is being used by at least 74 countries, by both ‘good guys’ and ‘bad guys’. It has also been mounted on all sorts of military and silly-vilian (civilian) vehicles.
U.S. Marines check-out a captured ZU-23-2 on the island of Grenada, 28OCT1983. U.S. Navy photo by Photographers Mate Second Class David Wujcik.
Iraqi ZU-23-2 during the early years of the Iran-Iraq War (1980-1988).
Iranian ZU-23-2 during the Iran-Iraq War (1980-1988).
Operation Praying Mantis; the U.S. attacks the Iranian navy during the Iran-Iraq War. U.S. marines check-out a ZU-23-2 on a captured Iranian offshore oil rig, 18APR1988. USMC photo by Corporal John Hyp.
Afghan ZIL-131 truck with ZU-23-2, under tow on Kandahar Airport, 17JAN2002. USMC photo by Captain Charles G. Grow.
Iraqi MTLB armed with ZU-23-2. USMC photo by Lance Corporal Jennifer A. Krusen, 11APR2003.
Iran loves the ZU-23-2 so much that in 2010 an eight barreled radar guided version (ZU-23-8?) entered production, it’s called the Mesbah-1.
In 2013, NATO-Greece modified their Soviet era BMP-1s by mounting ZU-23-2s on them.
November 2016, U.S. Army video (by Sergeant Jacob Holmes) of Ukrainian troops training with their ZU-23-2:
August 2017, U.S. Army promotional video (by Sergeant Anthony Jones) explaining the Ukrainian ZU-23-2:
On the left is a NATO-Romanian ground mount (towed) Oerlikon GDF 35mm guns, on the right is a NATO-Polish truck mounted ZU-23-2. U.S. Army photo by Gary Loten-Beckford, 06DEC2017.
NATO-Bulgarian ZIL-131 with ZU-23-2, during U.S. Army sponsored wargame Shabla 19. USA photo by Sergeant Thomas Mort, 12JUN2019.
Interestingly, during the false flag ‘Arab Spring’ rebellions that swept across North Africa and the Middle East, rebel/extremist groups were magically supplied with Toyotas equipped with ZU-23-2s. This photo (supposed taken in 2021) shows the new Libyan National Army with brand new ZU-23-2 equipped Toyotas.
Russian armored Ural ‘Tornado’ truck armed with ZU-23-2 (2A13) somewhere in the battle for Ukraine, April 2022.
In August 2022, the Houthis paraded their ZU-23-2 armed Toyotas in Sanaa, Yemen.
Russian remote controlled ZU-23-2 (2A13), June 2023. Photo via Russian Union of Mechanical Engineers.
Moldovan troops pose with their ZU-23-2, 13SEP2023. North Carolina Army National Guard photo by Staff Sergeant Brendan Stephens.
NATO video from March 2024, showing NATO-Poland’s upgraded ZUR-23-2, which can also launch anti-aircraft missiles:
Cold War to Battle for Ukraine:
ROMÂNIA Gardienii Cerului Gepard
End of the Cold War: 
Those decades when U.S. taxpayers supplied Russia with USAID!