The Soviet Model 1955 (M1955 / D-20) 152mm towed howitzer was developed in the late 1940s, too late to see combat asction in World War 2 (1939-1945). During its time as a frontline weapon system, the M1955 showed itself to have inherently strong reliability and firepower through the numerous wars that it was fielded across. The Soviet Union design bureau awarded the contract to Petrov Artillery and the M1955 was built in Yekaterinburg, a city central to Soviet arms making production during the war as many heavy factories were forced there after the German invasion in the west (Operation Barbarossa, June 1941).
The M1955 utilized the existing carriage of the D-74 system. Field trials proved the new arrangement well-designed and rugged enough during field trails. An 8 man crew was used for the gun section and an AT-S medium tractor was the prime mover along with the URAL-375 6x6 heavy truck. The barrel was made to the length of 17 feet and capped by a large, double-slotted baffle to help reduce recoil. A gun shield was mounted ahead of the wheels to protect the breech, recoil mechanism and crew. A firing pedestal was lowered to the grown before the weapon was engaged and the "split-trail carriage", also rested on the pedestal, provided full 360-degree traversal. The base gun mounting hardware gave -5 degrees to +65 degrees of elevation with a traverse of 58 degrees from centerline.
The main projectile used by the howitzer was the HE-FRAG (High-Explosive, FRAGmentation) weighing 95.92 lb which led to the sustained rate-of-fire of one round-per-minute. Special ammunition types included an AP (Armor-Piercing) shell of 237 lb that could penetrate 124mm (4.88") of armor thickness out to 1,000 meters (1,095 yards). Smoke and illuminating projectiles are also available along with a shell containing steel flechettes for anti-infantry use. Another form dispersed anti-personnel mines over a target area. Still another projectile type has become the "Krasnopol" semi-active, laser-guided smart munition.
A trained and experienced gunnery crew could stand to make 5 to 6 rounds-per-minute (1 rpm sustained). Range for HE-FRAG projectiles was 19,040 yards while Rocket-Assisted Projectile (RAP) landed as far out as 26,245 yards.
Despite its Soviet origins, the Russian military still relies to some degree on the M1955 series with as many as 1,000 guns still thought available. Efforts were made to modernize the design and keep it a viable battlefield solution for decades to come. The "Khitin" is an example of this, having added an automatic rammer and sporting an increased RoF to eight RPM.
China copied the gun as the "Type 66" and this variant went on to see deliveries all around the globe. Type 66 was made with few changes, making most Soviet parts interchangeable along with using all types of in-circulation 152mm ammunition. The Type 83 became a self-propelled version, most likely influenced by the Soviet 2S3 series vehicle. Similarly, the SPH 152mm M1974 of North Korea sees either the M1955 or Type 66 gun fitted to a tracked chassis.
Current operators range from Angola and Armenia to Vietnam and Yemen. Romanian models are designated A411. Former operates included Albania, East Germany / Germany, Finland and the former Yugoslavia (as the M84 "NORA" gun-howitzer).