Technically, I guess you are right about "regular" troop units not being used outside the borders of South Vietnam. However, I was in an Assault Helicopter Company (119th) that was assigned the job of moving small and large teams in and out of Laos. Many other units were assigned the same task on a rotating basis under the Johnson administration. We were regular American units of the 1st Aviation Brigade. LBJ was a liar and those who swear to his lies are liars, and I would urinate on his grave.
As for the comment above, I knew "snake-eater" types back in the 60's and 70's who, if the comment were made to them that way, might more than disagree with you. My experience in late 67 was that extracting units while under fire from the "trail" area was the exception rather than the rule.
The snake-eaters' beef is with my source (cited above). He was writing about his in-country experience from early 1969 to sometime in 1970. He emphasizes how quickly the insertion teams were picked up by the NVA (and they were regulars by that time) and talks about the pressure it put on the teams when they were trying to accomplish some task. Too, U.S. assets were well drawn-down by 1970, and he mentions that about half the fire bases that the U.S. had built by Tet had been abandoned in his operational area two years later. He discusses the impact that had on his group's operations.
Yes,and I can tell you that as a member of these teams,things had changed by late 68,and we were getting shot-up on a fairly regular basis. The reason for this seems to be that Tet-68 destroyed the VC,and the NVA started moving larger numbers of conventional troops down the trail for the build-up to take over.The smaller teams you refered to were recon teams,and the larger teams were the "Hatchet Force" platoons like used during "Operation Tailwind". I ran operations with both types of teams,and HF teams ALWAYS came out under fire. This is definitely true about the teams that launched out of Dak To.
You should also know that a lot of the teams had already made contact with NVA forces and been shot-up before a extraction was ever called for. They managed to escape from the NVA and call for a extraction after enduring several running gun battles. They were already sitting near a cold LZ before the call ever went out to bring the slicks in.
It is real soggy, leadpenny! LOL! A bunch of us have already been there, done that!