The Vietnam war lasted from 1968 to 1975. The American government tried to conceal the news of the killings. The events in My Lai had initially been covered up by local division command. In April 1969, nearly thirteen months after the massacre, Ron Ridenhour, a G.I. who had been with the 11th Brigade wrote letters to the President, a chairman of the Staff and the Secretary of Defense. In these letters Ridenhour described some of the events done by the soldiers at My Lai. This revealed Lieutenant Calley's plan to hide/conceal the massacre.