Staff Writer (Updated: 11/9/2016):
The ZPU-4 anti-aircraft system received its baptism of fire through operation by combat forces of China and North Korea during the Korean War (1950-1953). It saw considerable use against low-flying aircraft in the Vietnam War (1955-1975) where it became one of the most feared anti-aircraft weapons for American helicopters as the four-barreled arrangement could easily pierce critical components of the low-flying, slow-moving machines. Iraq managed a stock of these guns during the Persian Gulf War of 1991 and many of these fell to disuse after the American-led invasion of 2003. The ZPU-4 has been witnessed in combat service as recently as the Syrian Civil War (2011-Present).
Many countries have since replaced the aging ZPU-4 weapon - which relied on heavy machine guns - in favor of the ZU-23 anti-aircraft defense system - relying on 23mm autocannons. However, the ZPU-4 it still continues in frontline service with a handful of nations today (2011) including that of North Korea. The weapon went on to see extensive export to Soviet-aligned nations during the Cold War years, peak usage marking over 50 total operators. Chinese factories also locally produced variants of the gun system (under license) as the "Type 56" and "Type 58".
The ZPU-4 is typically seen in its towed/wheeled configuration integrating the weapon, crew seating, optics, and mounting hardware along a four-wheeled carriage to be towed by mover vehicle. The gun can also be removed for use as a stationary weapon or set atop the rear of a vehicle for mobile fire power. Besides its inherent value in tackling low-flying aerial targets, the system can prove equally-effective against light-armored vehicles while also having a tremendous psychological effect on unprotected infantry.
The ZPU-4 belongs to a family of Soviet anti-aircraft guns designated around the number of barrels in use. The ZPU-1 was given a single barrel while the ZPU-2 showcased a pair of guns. Appropriately, the ZPU-4 followed with its four gun arrangement.