He has served frequently as a consultant to the United States Department of State. In 2003, he testified before the 9-11 Commission (aka the National Commission on Terrorist Attacks Upon the United States). Journalist and academic Stephen Kinzer has called him "the most persistent" of "a small but dedicated group of scholars [who] have devoted considerable effort to uncovering the truth about events surrounding the 1953 coup" in Iran, an event so important (Kinzer believes) it "defined all of subsequent Iranian history and reshaped the world in ways that only now becoming clear."