"In 1968 during the war against Vietnam, the then major Colin Powell was dispatched to investigate charges of a massacre in My Lai. He concluded that while there might have been a few isolated incidents of killings of civilians there was no massacre. A letter from a soldier involved in the incident contradicted Powell's conclusion. Later investigations revealed that about 500 civilian men, women and children were murdered by American soldiers. Oddly enough, Powell on a visit to the Middle East in 2002 made similar remarks about a reputed Israeli massacre in Jenin (New Republic 17 April 1995 and Zunes 2003: 31)."
 http://www.globalcomplexity.org/Smoking%20Gun.htm