https://en.wikipedia.org/wiki/Phoenix_Program
I've read some of the eye witness descriptions of the CIA operatives involved, it's some of the heavier stuff I've read in my life, up there with torture perpetrated by Saddam's old regime.
Yes it was a dirty war on both sides, the Viet-Cong would also light civilians on fire with flamethrowers, villages and towns were mined and booby-trapped where US soldiers would be blown to pieces approaching them, but the thousands of civilians who farmed around the area and traveled back and forth to local villages went about their normal business unscathed knowing where all the mines were and never spoke up.
Those wiki sources aren't exactly an objective analysis and many seem sketchy. Reading further it seems that these were joint operations between the CIA, the SVR and MAC-V to eliminate the organizational structure of the VC in these certain province so US troops would not have to occupy them. Though I don't doubt that alot of "special interrogation methods" and unnecessary killings took place in the process of trying to find these people. They were using a loophole in the system where they could advise the SVR to use unconventional methods to get information out of these prospective targets where US forces couldn't because of the Geneva convention, pretty shady but believable stuff, and a typical eye for an eye scenario gone vastly overboard.
to usa
to be honest, many of these experiments have helped modern medicine, but still sucks to be one among these logs
Unfortunately this is how the US justice system encourages criminals to speak up. Basically if they tell the truth and give up information their sentence is lessened, and for high priority cases of great importance the plea bargains are often more generous for the sake of finding out all the facts and they might even walk away free as part of the deal if they give up all the information they are looking for.