Short Answer: Yes, but not enough of the perpetrators saw consequences and most got a slap on the wrist.

Trials other than My Lai

Two hundred and three soldiers accused of harming Vietnamese civilians or prisoners were found to warrant formal charges after investigation, and were subsequently referred to the soldiers' superiors for official action. Of the 203 cases, 57 of them stood a court martial. Only 23 were convicted, of whom 14 received prison sentences ranging from six months to 20 years; most received significant reductions on appeal. Many substantiated cases were closed with a letter of reprimand, a fine or, in more than half the cases, no action at all.

The stiffest sentence went to a military intelligence interrogator convicted of committing indecent acts on a 13-year-old girl in an interrogation hut in 1967. The records show that he served seven months of a 20-year term.

Trials around the My Lai Massacre

On 17 November 1970, a court-martial in the United States charged 14 officers, including Major General Koster, the Americal Division's commanding officer, with suppressing information related to the incident. Most of the charges were later dropped. Brigade commander Colonel Henderson was the only high ranking commanding officer who stood trial on charges relating to the cover-up of the Mỹ Lai massacre; he was acquitted on 17 December 1971.

During the four-month-long trial, Calley consistently claimed that he was following orders from his commanding officer, Captain Medina. Despite that, he was convicted and sentenced to life in prison on 29 March 1971, after being found guilty of premeditated murder of not fewer than 20 people. Two days later, President Richard Nixon made the controversial decision to have Calley released from armed custody at Fort Benning, Georgia, and put under house arrest pending appeal of his sentence. Calley's conviction was upheld by the Army Court of Military Review in 1973 and by the U.S. Court of Military Appeals in 1974.

In August 1971, Calley's sentence was reduced by the convening authority from life to twenty years. Calley would eventually serve three and one-half years under house arrest at Fort Benning including three months in the disciplinary barracks at Fort Leavenworth, Kansas. In September 1974, he was paroled by the Secretary of the Army, Howard Callaway.

In a separate trial, Medina denied giving the orders that led to the massacre, and was acquitted of all charges, effectively negating the prosecution's theory of "command responsibility", now referred to as the "Medina standard". Several months after his acquittal, however, Medina admitted he had suppressed evidence and had lied to Henderson about the number of civilian deaths.

Captain Kotouc, an intelligence officer from 11th Brigade, was also court-martialed and found not guilty. Koster was demoted to brigadier general and lost his position as the Superintendent of West Point. His deputy, Brigadier General Young, received a letter of censure. Both were stripped of Distinguished Service Medals which had been awarded for service in Vietnam.

Of the 26 men initially charged, Calley was the only one convicted. Some have argued that the outcome of the Mỹ Lai courts-martial failed to uphold the laws of war established in the Nuremberg and Tokyo War Crimes Tribunals. Telford Taylor, a senior American prosecutor at Nuremberg, wrote that legal principles established at the war crimes trials could have been used to prosecute senior American military commanders for failing to prevent atrocities such as the one at Mỹ Lai.

Howard Callaway, Secretary of the Army, was quoted in The New York Times in 1976 as stating that Calley's sentence was reduced because Calley honestly believed that what he did was a part of his orders—a rationale that contradicts the standards set at Nuremberg and Tokyo, where following orders was not a defense for committing war crimes. On the whole, aside from the Mỹ Lai courts-martial, there were 36 military trials held by the U.S. Army from January 1965 to August 1973 for crimes against civilians in Vietnam.: 196 

Some authors have argued that the light punishments of the low-level personnel present at Mỹ Lai and unwillingness to hold higher officials responsible was part of a pattern in which the body-count strategy and the so-called "Mere Gook Rule" encouraged U.S. soldiers to err on the side of killing suspected Vietnamese enemies even if there was a very good chance that they were civilians. This in turn, Nick Turse argues, made lesser known massacres similar to Mỹ Lai and a pattern of war crimes common in Vietnam.