 The actual play of the war game involved 30 to 35 participants.There are four or five simulations per year, solicited secretively from the State Department, the Central Intelligence Agency, and major military commands.While earlier Sigma War Games had considered whether U.S. combat troops should be committed to the Vietnam War, Sigma I-65 was held just after U.S. Marines had landed in Danang, Republic of South Vietnam on 8 March 1965.