IT was 50 years ago tomorrow that the USA reeled at the shock news that the military authorities were to be investigated for colluding in the cover-up of a war crime like no other.

The My Lai Massacre took place on March 18, 1968, when hundreds of Vietnamese civilians were murdered in cold blood by American troops.

From the start, the US authorities were determined to cover up what had happened – and they very nearly succeeded.

IF WE ALL KNOW ABOUT IT THEN WHY TALK OF A COVER-UP?

IT seems almost incredible to us now in these days of ubiquitous smartphones, but no-one actually filmed the events in and around My Lai. That greatly assisted the US military leaders who, with the collusion of highly placed people in the US government, set about containing news of the massacre. It was portrayed from the start as a successful mission against Viet Cong insurgents with some “unfortunate” civilian casualties.

We know that there was a cover-up but even now, 50 years on, we still do not know how many people in the US military and government were involved. We know as much as we do thanks to the efforts of three brave men, a whistleblower Ronald Ridenhour, reporter Seymour Hersh and investigator General William Peers.

SO WHAT HAPPENED AT MY LAI?

IN brief, 100 US soldiers marched into the hamlets to locate and kill Viet Cong (VC) guerrillas. The VC had already gone, but at 7.30am Lieutenant William Calley Jnr entered My Lai and started firing at civilians. His platoon followed and within minutes the operation had turned into an orgy of rapine and gruesome bloody murder in which 504 men, women and children, including babes in arms, were killed.

US helicopter pilot, Warrant Officer Hugh Thompson, stopped the massacre by landing his helicopter between the villagers and their murderers.

WHO STARTED THE COVER-UP?

THOMPSON reported the massacre as soon as he got back to base. There then began an elaborate official process of covering up what had really happened.

The press crops were briefed that Medina and his men “tangled with Communist forces threatening the northern city of Quang Ngai” and that “US spokesmen “reported 128 guerrillas slain in the bitter fighting”. The army PR people would only say details were “sketchy”.

For months, rumours circulated of a massacre of civilians, but even the most bitter opponents of the Vietnam War would not believe US troops could act that way and it appeared the massacre would stay secret.

The cover-up unravelled when, early in 1969, Vietnam veteran Ridenhour wrote to politicians alleging the massacre after hearing about it from fellow helicopter gunners. Young reporter Hersh heard about the letter, made inquiries and broke the story of My Lai. Calley was arrested and charged with murder, but Hersh then exposed the cover-up.

On November 24, 1969, General William Peers was appointed to carry out an inquiry and he did a brilliant forensic job detailing exactly what happened in My Lai and showing how senior military figures colluded to cover up the massacre. Some 25 officers and men were charged but only Calley was convicted. President Richard Nixon would later commute his 10-year sentence to three years.

WHAT RELEVANCE HAS THE COVER-UP NOW?

AS Nixon found out over Watergate, it’s often not the crime but the cover-up that gets you. And as current incumbent Donald Trump is finding over Ukrainegate, you can only hoodwink the USA so much and when your cover-up is blown, the damage is very much the greater.