How long does it take the US government to release documentation about atrocities in which US military forces killed unarmed civilians, women and children? In the case of Vietnam, it's taken almost 40 years. The 1968 My Lai massacre became public in 1969, but officials at the time said My Lai was an "isolated incident"–the same thing we hear about atrocities today in Iraq and elsewhere. After that, GIs described dozens of other My Lai-style atrocities in which they said they had taken part. Those GIs were called liars and traitors, and no one was ever punished for any of the events they described.

Now the Los Angeles Times has published a page one story, "Vietnam Horrors: Darkest Yet," based on official government documents detailing 320 incidents of Vietnam war atrocities that were confirmed by army investigators. The documentation, according to the Times, comes from "a once-secret archive assembled by a Pentagon task force in the early 1970s." This "Vietnam War Crimes Working Group" archive, 9,000 pages long, was discovered by Nick Turse, who was doing research for a Ph.D. dissertation as a student at Columbia University. Turse shares the byline on the Times report with staff writer Deborah Nelson.

The stories are terrible. "Kill anything that moves" – that's what one company of American soldiers was told when they set out on a sweep of the rice paddies on Vietnam's central coast in February 1968, according to Jamie Henry, at the time a 20-year old medic. So they shot and killed 19 unarmed civilians, women and children. When Henry got home to California, he held a news conference describing the slaughter, but there was no official response. Now we learn that the army did investigate his report — and concluded it was accurate – but did nothing to punish the guilty.

The official line that abuses were "confined to a few rogue units" is demolished by the material Turse discovered. Atrocities were committed, according to the Times, by "every army division that operated in Vietnam." They found a pattern of "recurrent attacks on ordinary Vietnamese–families in their homes, farmers in rice paddies, teenagers out fishing," who were "murdered, raped and tortured with impunity" by American soldiers.

Military investigators documented seven large-scale massacres between 1967 and 1971 in which at least 137 civilians were killed. They described 78 other attacks on civilian noncombatants in which US troops killed at least 57, wounded 56 and sexually assaulted 15. They described 141 incidents of torture of civilians, including the use of electric shock.

The evidence against 203 soldiers was strong enough for the military to bring formal charges of war crimes. According to the Times investigation, 57 were court-martialed and 23 convicted – about ten percent. Fourteen were sentenced to prison for terms ranging from six months to 20 years, but most appealed and won significant reductions. The longest sentence, 20 years, went to an interrogator convicted of "committing indecent acts on a 13 year old girl in an interrogation hut." He served only six months.

Army investigators came to no finding about 500 other reports of atrocities, some of which described extensive killing. One sergeant reported in a 1970 letter about a pattern of American soldiers murdering civilians in the Mekong Delta in 1970. "I am trying to tell you about 120-150 murders, or a My Lay [sic] each month for over a year," he wrote. The Times reported that "there is no evidence in the files that his complaint was investigated further."The extensive LA Times report includes details about particular incidents and online links to documents including statements by participants in atrocitiesand a memo from White House counsel John Dean.

Of course this archive deals only with Vietnam atrocities that the army investigated. Doubtlessly hundreds, perhaps thousands of other incidents were not reported – for example former Senator Bob Kerrey's role in killing unarmed Vietnamese villagers in the Mekong Delta in 1969, first reported in 2001.

The Fourth Geneva Convention of 1949 and official US policy require the protection of civilian non-combatants in wartime. Public opinion in the US turned against the Vietnam war in part because My Lai suggested it was a war on the Vietnamese civilian population rather than a defense of freedom and democracy, as Nixon claimed. 125 eyewitness reports of atrocities were presented at the "Winter Soldier Investigation" in Detroit in 1971, organized by Vietnam Veterans Against the War.Senator John Kerry, an anti-war Vietnam vet at the time, described those hearings in his Senate testimony in 1971.

The only recent report confirming Vietnam atrocities was the "Tiger Force" story that won the Toledo Blade a Pulitzer prize in 2004. Tiger Force was an elite unit of the 101st Airborne division that, according to the Blade, "killed unarmed civilians and children during a seven-month rampage." That story also revealed that army officials failed to stop the atrocities and then failed to prosecute soldiers found to have committed war crimes. That story recently was told in a book, Tiger Force: A True Story of Men and War. The new revelations in the LA Times are much broader and deal, not with a single unit, but rather with every division that fought in Vietnam.

As for Iraq today, reports of war crimes committed there by US forces have appeared recently. The LA Times has been covering a family of four in Baghdad murdered by US military, including a 14-year-old girl apparently raped first, and her 5-year old sister shot in the head. The incident has gotten a lot of coverage in Iraq.

The records of the Vietnam War Crimes Working Group that Nick Turse discovered in the National Archives, and that provided the basis for the L.A. Times story, have now been closed to the public, on the grounds that they contain personal information exempt from release under the Freedom of Information Act.

The Vietnam documents inevitably raise the question of whether we are getting the full story now about Iraq, and whether the military has changed its Vietnam-era practices of secret investigations of atrocities concluding with no punishment for the guilty. We may have to wait another 40 years to find out.