Designed in the early 1960s, the BM-21 Grad 122mm Multiple Rocket Launcher is a Soviet truck-mounted 122mm multiple rocket launcher and a M-21OF rocket. The “BM” in its name stands for boyevaya mashina, or combat vehicle, and its common name of “Grad” means, “hail.” The combination of the BM-21 launch vehicle and the M-21OF rocket is considered the complete M-21 Field Rocket System; this complete system is more commonly known as the Grad multiple rocket launcher system. In NATO countries this system, or only the launch vehicle, is known as the M1964.

The M-21 Field Rocket System, complete with BM-21 multiple rocket launcher system, entered service with the Soviet Army in 1963 to replace the BM-14 system. The BM-21 itself is comprised of the Ural-375D six-by-six truck chassis that has been fitted with a 40-tube bank of launch tubs that are arranged in a rectangular shape that may be turned from the cab. A 180-horsepower V-8 gasoline engine with a maximum road speed of 75 km/h (47 mph) powers this vehicle. It has a road range of up to 750 kilometers (470 miles) and can ford depths of up to 1.5 meters (4 ft. 11 in).

The BM-21 may be operated and fired from inside of the cab, or it may be fired remotely using a cable set at a distance of up to 60 meters. The launcher is transversed forward towards the cab when traveling and fires using two stabilizing jacks that are found near the rear of the vehicle. Special electric generators power the launcher. This MRL is able to fire all of the 40 rockets in 6 seconds, or fire each individually. A three-man crew can replace the system and have it fire-ready in approximately three minutes.

Many adaptations of the launcher were and still are produced by several countries, including China, the former Czechoslovakia, Egypt, Iran, North Korea, Poland, and Romania. There are numerous Soviet Union variants of the BM-21 Grad 122mm multiple rocket launcher available, including:

• BM-21-1

• 2B17

• 9P138 “Grad-1”

• BM-21V “Grad-V”

• 9A51 “Prima”

• “Grad-P” Light portable rocket system

• BM-21PD “Damba”

• A-215 “Grad-M”