Should have stipulated US forces. The 72 Nguyen Hue (their word) or the Easter Offensive (ours) was the biggest battle of the war and PAVN used and lost several dozen AFVs. Don't think anybody really knows because at places like An Loc B-52s obliterated square miles of territory. Was thinking of writing a book about that campaign and interviewed Turley and Miller, two of our top advisers in the An Loc campaign. Both said if PAVN had thrown away the Soviet book and bypassed An Loc that Saigon would have been very vulnerable to capture. "Smart" weapons made their bigtime debut in that campaign (guess TOW was sort of smart - the laser guided bombs used in the North were brainy for the time). So I suppose LAWs would have had victims - there was a lot of very close fighting at several locations. But I doubt many. I interviewed a lot of 25th Division vets and several used LAWs and found them very useful on occasion but noted they were glad the targets weren't tanks. (Depressing to read about debates over Hanoi's intentions at Khe Sanh or in 1972. We just never got it. PAVN was great exponent of hitting hard, let the fur fly, and see what comes up. In my humble, Hanoi and company was the most skilled enemy the US ever engaged. Surely they screwed up more than once but nobody has ever fought a perfect war.)
I'm not really sure about 1968. The fighting around Khe Sanh was a nasty business and we weren't on the winning side of every skirmish - that's not good for record keeping. Wikipedia (which has a dicey entry on the Easter Offensive) notes in the PT-76 entry that LAWs did not do well at at Lang Vei and it was a recoilless rifle that did the dirty work. (As earlier noted recoiless rifles were often found "dug in" throughout Vietnam.) I guess we didn't give ARVN the ONTOS during "Vietnamization" - Not sure why - I'd guess they would have found use for them. Maybe we figured a dug-in RR was more effective. A few of those might have come in handy in 72.
The Army didn't like the LAW as an anti-tank weapon and intended on retiring it but Congress got stingy after "Peace" in Vietnam. We got some AT4s from Sweden but found there were precious few tanks to fight. As I understand it, LAWs, being nice and light, found a second wind in Afghanistan and Iraq for hitting caves etc. Not long ago I talked to an old friend who served as a 17 year old Marine in WWII, joined the Army and was with Task Force Smith in Korea and a province adviser in Vietnam. For thirty years the guy's been toasting Army for not having a really good US made Panzerfaust-like weapon. (Comment on the LAW - "worthless on a modern battlefield.") He said during the Korean battles in 1950 that the bazooka was seriously flawed and the soldiers knew it and that if infantry had their own anti-tank weapon that worked well they would be more inclined to stick around. His point is that if you run into a tank you don't necessarily have the time to get in gunships or aircraft and considers Army doctrine (ie unsupported US infantry will rarely see a tank to be a matter of faith. The Army's been right - so far.
Eric