 His recollection is that Sigma I-63 ended in a fictional 1970 with 500,000 American troops locked in a stalemate in Vietnam, and conscription riots in the United States.According to another account, after the five-day game played out a hypothetical ten year Vietnam War, the North Vietnamese had increased their infiltration into South Vietnam despite the presence of 600,000 U.S. servicemen.U.S.