Members of the unit say it was impossible for them to tell who was an enemy fighter and who was a peaceful villager.
The young lieutenant who commanded the unit, James Hawkins, now 63, says he and his men learned to smell the enemy or anyone who might pose a threat.
"I can't describe how this really, the smell was," he told ABCNEWS. "But it was a distinct, odor, you know, if they had been there, you'd been down a trail. You, you could smell where they'd been there recently."
Causey recalled catching a group of Vietnamese by surprise, causing them to come out of their hut with their hands up. When Causey and fellow soldiers called the platoon leader to find out what they should do with them, "a minute or so later he responded that they should be shot. So we took them over to the wall and lined them up and we shot them," said Causey, who was never investigated nor charged with any wrongdoing.
Until now, the most infamous war crimes investigation of the Vietnam War was the My Lai massacre in March 1968, during which U.S. soldiers killed as many as 400 Vietnamese civilians. Of the soldiers tried, only Lt. William Calley was convicted and sentenced to life in prison. His term was eventually reduced to 10 years in prison, and he was later paroled in 1975 after serving three-and-a-half years under house arrest.
"The Tiger Force case was the longest war crimes investigation of the Vietnam War," said Sallah. "It was four-and-a-half years. My Lai pales in comparison in terms of the length of time it took to investigate it."
The Army began its investigation into Tiger Force in 1971, four years after the incidents, after a tip from a fellow battalion member who said a Tiger Force soldier had severed the head off an infant to obtain a necklace from the baby's neck.
The Blade obtained the final report written by the Army's own investigators, which concluded that 18 Tiger Force members committed war crimes, including at least three murders.
It was up to Army commanders to decide whether to court-martial any of the individual soldiers. In the end, no soldier was ever prosecuted.
A lead investigator, who asked that his name not be used, told ABCNEWS, "Commanders have final jurisdiction of whether or not to file a case.
"I filed my report with distribution to all the commanders [at the Criminal Investigation Department] and that was the end of their involvement. I don't write an indictment," he said.
Doyle, who himself was investigated for murder and aggravated assault, said he was proud of what he did in Vietnam.
"I was killing them in self-defense," said Doyle. "The way I seen it, because of the fear tonight, tomorrow, the foot mines, the situation."
Doyle, who received numerous decorations for bravery, admitted killing his own Vietnamese translator, a captured North Vietnamese soldier.
"I'm going to trust my men's lives to him? That's something you dream up in Washington, D.C.," said Doyle.
Vietnamese Have Not Forgotten
Some 36 years later in Vietnam, the people who live in the same villages where Tiger Force came through want to know why the U.S. government has never admitted what happened.
The villagers have not forgotten.
Kieu Trac remembers when Tiger Force soldiers rampaged through the tiny hamlet of Hanh Tin. He says 10 elderly farmers were killed by the Americans. Trac hid in his hut until the soldiers left the village, and then he buried the bodies.