The S-23 is a early Cold War era heavy gun of Soviet origin. It was developed after World War 2 to provide Soviet forces with the ability for long range shelling. In the West it was referred to as the 203mm M1955 gun, although its actual caliber is 180mm. When introduced the S-23 had a phenomenal range, good accuracy and reasonable volume of fire. Modern 155mm 52-caliber howitzers offer a similar range and higher rate of fire, but at reduced cost, crew requirement and weight.

The 180mm 49-caliber ordnance with pepperpot muzzle brake was derived from the older Chapayev naval gun. The gun is mounted on a heavy split trail carriage. The carriage has a single axle with four wheels. A 16 man crew is required for normal operations. No gun shield is provided since the S-23 is to be used well behind the frontline.

The S-23 fires powerful 180mm shells at high velocity at ranges up to 30.4 km. Types of shell include high explosive and concrete piercing. Reportedly a nuclear round was deverloped as well. A rocket assisted projectile introduced in the early 1970's extends the maximum range out to 43.8 km. The maximum rate of fire is 1 round per minute. Sustained fire reduces the rate of fire to 1 round every 2 minutes. Accuracy is reported to be good, even at maximum range.

The S-23 is a large and heavy gun and as such is difficult to transport. In travelling mode a two wheel dolly is used and the ordnance is withdrawn to the rear in order to reduce overall lenght. A heavy truck or preferably a tracked prime mover is used to tow the gun. In Soviet service the AT-T artillery tractor was used.

The S-23 was adopted by Soviet forces and used at a ratio of 12 weapons per heavy artillery brigade. It was exported to several Soviet allies and was used during several Middle East conflicts. In Soviet service the S-23 was replaced by the self-propelled 2S7 Pion and heavy rocket artillery such as the FROG-7.