Richard Nixon was a secretive paranoid bigoted sonofabitch. But we never knew the half of it: It turns out his administration waded neck-deep into efforts to sink a war-crimes investigation against U.S. soldiers who notoriously butchered an entire village in Vietnam.

CBS News says new research by historians into old notes collected at the Nixon Presidential Library suggests that years before Watergate went down, Tricky Dick wanted to use nasty tactics with plausible deniability to help bury what happened in the ville of My Lai in 1968:

The documents, mostly hand-written notes from Nixon's meetings with his chief of staff H.R. "Bob" Haldeman, lead some historians to conclude that President Richard Nixon was behind the attempt to sabotage the My Lai court-martial trials and cover up what was becoming a public-relations disaster for his administration.

One document, scribbled by Haldeman during his Dec. 1, 1969, meeting with Nixon, reads like a threatening to-do list under the headline "Task force - My Lai." Haldeman wrote "dirty tricks" (with the clarification that those tricks be "not too high a level") and "discredit one witness," in order to "keep working on the problem."

"Haldeman's note is an important piece of evidence that Nixon interfered with a war-crime prosecution," says Ken Hughes, a researcher with the University of Virginia's Miller Center Presidential Recording Program.

Haldeman knew a thing or two about dirty tricks; he went to federal prison after being convicted on charges of perjury and obstruction of justice in connection with the Watergate scandal.

My Lai's devastation is one of the enduring, iconic moments of America's military involvement in Vietnam. A company of U.S. soldiers, led by Lt. William Calley, killed between 350 and 500 Vietnamese in cold blood and razed their village, essentially erasing it from the face of the earth, as captured in these images by Army photographer Ronald Haeberle (warning: graphic images):

The carnage was interrupted at one point by two three helicopter crewmen, who attempted to save some of the villagers and evacuate casualties. Those men's testimony was reportedly one target of Nixon's dirty tricks.

It's unclear whether any of Nixon's darker My Lai plans came to fruition, but he was deeply involved in the case. Incredibly, many in the U.S. either denied that American soldiers were capable of such evil or wrote the acts off as justifiable. Of the 26 men charged in connection with the massacre, only one—Calley—was convicted of a crime. He was sentenced to life in prison for killing more than 20 civilians.

But Nixon ordered that Calley be transferred, and he had his sentence commuted; he eventually served three and a half years on house arrest before being paroled.

The entire mass-killing might have remained unknown by the U.S. public, in fact, if not for the investigative work of a young reporter named Seymour Hersh, who brought the killings to light, and in doing so changed many Americans' attitudes towards the war, and towards the behavior of their own soldiers.

Even more incredibly, Haldeman's incriminating notes actually were released to the public in 1987, but only now have historians begun to confirm their significance. The helicopter crewmen who saved some of My Lai's villagers supposedly knew about the Nixon notes awhile back—and one says he was flummoxed "there was no reaction at all" from chroniclers when the notes were unearthed. "I was amazed. I thought, 'Are you kidding me?'"

[Photo credit: AP]