Mark Greaney has a degree in international relations and political science. In his research for the Armored novels and the Gray Man novels, including The Chaos Agent , Burner , Sierra Six , 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 thirty-five countries and trained alongside military and law enforcement in theuse 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 coauthored Locked On , Threat Vector , and Command Authority.