Schematic of SA-7 Grail missile, type used against US/ARVN chopper forces. Soviet production began in 1970 and secretly supplied to North Vietnamese in 1972.

SA-7 Grail | Wiki

Weapon is a man-portable, shoulder-fired, low-altitude surface-to-air missile launcher with high explosive warhead and passive infrared homing guidance. Performance-wise, Grail is comparable to US FIM-43 Redeye missile.

FIM-43 Redeye | Wiki

SA-7 and its variants now proliferate across conflicts worldwide given Soviet/Russian liberal dissemination of such technologies.

1st Battalion 22nd Infantry with captured Iraqi SA-7 | 1-22Infantry.org

BTW, SA-7 Grail is a US/NATO designation, official Soviet name is 9K32 Strela-2 (Arrow 2). US practice of creating separate nomenclature for foreign (non-Latin alphabet) weapon systems began in WW2 when American intelligence teams found it difficult memorizing Japanese aircraft names, thus they used American boy and girl names for ease of recall (ex. Mitsubishi G4M Isshikirikkou bomber = Betty, Nakajima Ki-43 Hayabusa fighter = Oscar, Yokosuka D4Y Suisei dive-bomber = Judy).

WW2 Japanese Aircraft Allied Designations | UweM

NVA trooper in propaganda-promo shot for 9K32 Strela-2 (Arrow 2) surface-to-air missile. Photo indicative of missile size and man-portability.

9K32M Strela-2 | FAS.org

Strela caused great havoc among US/ARVN chopper crews, some tactics were developed to offset its advantage (ex. L-scoop engine exhaust), but like old back-alley street fight saying "Best way to survive a knife fight is never to get into one"... proverb is also true of avoiding encounters with Strela.

But bemoan not, for US would repay Soviets "in kind" early-1980s when CIA supplied US Stinger missiles to Afghanistan Mujahideen groups against Soviet chopper transports and gunships, destroying about 270 aircrafts throughout 10-year Soviet occupation.

CIA activities in Afghanistan | Wiki

FIM-92 Stinger | Wiki

But, modern saying "no good deed ever goes unpunished", fearing US Stinger missiles in Afghanistan and Pakistan would fall into Islamic terrorist groups ( which would wreck chaos onto military and civilian air traffic alike) CIA has been "buying back" the Stingers since early-2000 at a cost of $200,000 to $300,000 each.

What About the Taliban's Stingers? | NYTimes.com

Any consolation, Soviet Strela missiles proliferate 3rd world nations as much as their vaunted AK-47 assault rifles, especially in Middle East. Infamous incident was 28 Nov 2002 Mombassa-Kenya when 2 Strela-7 missiles were fired against Boeing 757 airliner carrying 261 Israeli vacationers.

2002 Mombasa attacks | Wiki

Mombassa missile attack (counter opinion) | JICB

How to Avoid a Heat-Seeking Missile | Wired.com

Before SA-7 missile threat, major US chopper nemesis was Soviet-made heavy caliber weapons. This one captured and used in gunnery training. Soldier wearing US Special Forces dapple camouflage pattern.

Soviet DShKM 12.7-mm Heavy Machine Gun | Lcompanyranger.com

Soviet DShKM 12.7mm (51-Caliber) Heavy Machine Gun is a gas-operated, belt-fed, air-cooled, fully automatic-only weapon, firing from open-bolt position.

Developed by Soviets in 1938, NVA used such weapon against low flying aircraft and chopper landing zones. BTW, DShK is Soviet abbreviation for Degtyaryov-Shpagin or Large-Caliber weapon.

DShK 1938 | Wiki

7 Apr 1972, NVA overran Quan Loi airfield circa 5 miles northeast of An Loc, cutting off city's only airbase.

Quan Loi Airstrip, Vietnam 1968 | 1DI

Quan Loi Air Field, 1969-70 | 1DI

19 Apr - 11 Jul 1972, NVA lay siege to An Loc city itself, cutting off ground supply link.

Thus, USAF supplied city defenders via air drops, as shown in photo. ARVN reinforcements were air-mobile inside siege lines via US Huey choppers with Cobras provided escorts.

History of Quan Loi Airstrip, RVN | 1DI

Schematic of NVA armor assault on 11 May 1972, which was its deepest city penetration.

Solid lines are ARVN main defense posts, Outlines are NVA thrusts from northern via Highway 13 (QL-13) and western (Route 246) sectors.

NVA attempted to pincer and split ARVN defenses at city center. These armor street battles have been replicated many times in history, be it Budapest - Berlin - Breslau in 1945 or Gronzy 1995.

Since NVA armor outran its accompanying infantry, its tanks ran into torrent of ARVN & US sapper teams and anti-armor LAW weapons, while USAF incessantly carpet bombed NVA assembly points north of An Loc.

They Were Good Ol' Boys - An infantryman Remembers An Loc and the Air Force | Maxwell.af.mil

An Loc city aerial view during NVA siege, large smoke cloud bellowing on left, majority of buildings were mere empty shells or roofless hulks after successive NVA artillery attack.

Battle of An Loc | AnLoc.org

For 11 May 1972 attack alone, NVA plastered city with 7,000-round artillery barrage before unleashing armor assault.

Recollections from Vietnam | Petester.com

An Loc | Wiki

1 May 1972 : Despite staunch US/ARVN defense in southern An Loc and central Kontum regions, NVA in concentrated armor thrusts overran 15 ARVN Fire Support Bases in Quang Tri province - northern South Vietnam. ARVN defense collapsed into mass retreat.

FSB#6 Layout - US 1/92nd Field Artillery | BraveCannons.org

Note : NVA used sporadic armor units in previous battles, such as 1968 attack on US Marine base at Khe Sanh, but 1972 was first time NVA deployed massive tank assaults into South Vietnam.

Battle of Khe Sanh 1968 | Wiki

Photo inset shows grisly scene on QL-1 highway near Truong Phuoc bridge, what Vietnamese call "Highway of Horror".

Area fell to NVA offensive as South Vietnamese soldiers and civilians alike crowded only eastward escape route out of Communist pincers. This panic-stricken column feared Communist massacres, like what happen to Hue city in 1968 when NVA/Viet Cong dragged 8,000 people into surrounding jungles and executed captives into open burial pits. They were still finding mass unmarked jungle graves as late as 1972.

Massacre at Hue | Wiki

Hue Massacre 1968 | VNAFmamn.com

NVA destroyed Truong Phuoc bridge, trapping thousands in salient as they systematically plummeted artillery and mortar fire into the crowds. 2 months after massacre, bodies of about a thousand men-women-children strewn across landscape when ARVN counter-attacked and retook region. Other wretched scenes were the survivors, either too weak to travel or unwilling to leave their dead family members behind, stay with their remains until proper burial was achieved.

Highway of Horror - Vietnam 1972 | vnafmamn.com

THE STREET OF HORROR | VQC

South Vietnamese established Buddhist memorial at locale in 1972, but was destroyed by North Vietnamese Communists in 1975, lest their misdeeds be too publicized. Nevertheless, memorial services still observed by Vietnamese diaspora in Americas - Europe - Australia.