The BM-21 "Grad" is a self-propelled 122 mm multiple rocket launcher designed in the Soviet Union. The system and the M-21OF rocket were first developed in the early 1960s, and saw their first combat use in March 1969 during the Sino-Soviet border conflict. BM stands for boyevaya mashina, and the nickname grad means "hail". The complete system with the BM-21 launch vehicle and the M-21OF rocket is designated as the M-21 field-rocket system and is more commonly known as a Grad multiple rocket launcher system.