The BM-21 "Grad" is a Soviet truck-mounted 122 mm multiple rocket launcher. The weapons 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 (Russian: combat vehicle), 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. The complete system is more commonly known as a Grad multiple rocket launcher system. In NATO countries the system (either the complete system or the launch vehicle only) was initially known as M1964. Several other countries have copied the Grad or have developed similar systems.