The danger these guys routinely faced was absolutely insane. Especially when you consider evidence that MACV-SOG/CIA operations were sometimes compromised by North Vietnamese moles within the organization.
While American teams penetrated into Laos and Cambodia most of the teams sent into the North were Vietnamese--for obvious reasons. Too many of them, and a number of the US teams, disappeared without a trace.
Years after the war it became clear they'd been captured or wiped out. I can tell you from personal experience that treachery was not uncommon and the North had infiltrators in many places (including one of our attached Regional Force units).
Incidentally, as of recently, some of the declassified but redacted documents I've read indicate that many former MACV-SOG Vietnamese operatives never got out of the country in 75 or subsequent years and are still in some danger of being exposed.
Here's a Newsweek article from '05 that cites former US intelligence officials and Communist sources:
"...Pham was a key double agent in an operation that led to the capture or deaths of scores of CIA and U.S. military–controlled spies for nearly a decade during the war..."
"'...ARES was a singleton agent infiltrated into North Vietnam by the agency," says Walter McIntosh, a former chief of Vietnam operations for the CIA. "He was taken over by MACV-SOG, which failed to detect that [he] had fallen under North Vietnamese control." McIntosh recalls that he was so certain Pham had been doubled that he refused to assist the military unit on any more resupply missions to him. "I wrote a 12-page dispatch citing the evidence of ARES being in NVN control and what special stuff had been compromised," he says..."
New Vietnam Spy Tale Sheds Light on How the U.S. Lost the War
Keep in mind, the Communist sources exaggerate the success of their operations. But it highlights the double-peril MACV-SOG teams faced jumping the fences.
And the
Newsweek title is way overboard. 1. We didn't lose the war; it was "discontinued" by public pressure and politics. And 2., the disruption of clandestined US/SVN operations was never impactful enough to derail the entire war effort, nor, for that matter, was any NVA/VC military action.