Soviet Union in Vietnam War: Soviet ships in the South China Sea gave vital early warnings to NLF forces in South Vietnam. The Soviet intelligence ships would pick up American B-52 bombers flying from Okinawa and Guam. Their airspeed and direction would be noted and then relayed to COSVN headquarters. COSVN using airspeed and direction would calculate the bombing target and tell any assets to move "perpendicularly to the attack trajectory." These advance warning gave them time to move out of the way of the bombers and while the bombing runs caused extensive damage, because of the early warnings from 1968–1970 they didn't kill a single military or civilian leader in the headquarter complexes.

During the Vietnam War, The Soviet Union supplied North Vietnam with medical supplies, arms, tanks, planes, helicopters, artillery, anti-aircraft missiles and other military equipment. Soviet crews fired USSR-made surface-to-air missiles at the B-52 bombers, which were the first raiders shot down over Hanoi. Fewer than a dozen Soviet citizens lost their lives in this conflict. Following the collapse of the Soviet Union in 1991, Russian officials acknowledged that the Soviet Union had stationed up to 3,000 troops in Vietnam during the war.

Some Russian sources give more specific numbers: the hardware donated by the USSR included 2 000 tanks, 7 000 artillery guns, over 5 000 anti-aircraft guns, 158 surface-to-air rocket launchers. Over the course of the war the Soviet money donated to the Vietnamese cause was equal to 2 million dollars a day. From July 1965 to the end of 1974, fighting in Vietnam was attended by some 6,500 officers and generals, as well as more than 4,500 soldiers and sergeants of the Soviet Armed Forces. In addition, military schools and academies of the USSR began training Vietnamese soldiers – more than 10 thousand people