Mark Greaney has a degree in international relations and political science. In his research for the Gray Man novels, including Relentless, One Minute Out, Mission Critical, Agent in Place, Gunmetal Gray, Back Blast, Dead Eye, Ballistic, On Target, and The Gray Man, he traveled to more than fifteen countries and trained alongside military and law enforcement in the use of firearms, battlefield medicine, and close-range combative tactics. With Marine Lt Col Rip Rawlings, he wrote the New York Times bestseller Red Metal. He is also the author of the New York Times bestsellers Tom Clancy Support and Defend, Tom Clancy Full Force and Effect, Tom Clancy Commander in Chief, and Tom Clancy True Faith and Allegiance. With Tom Clancy, he co-authored Locked On, Threat Vector, and Command Authority.