Mark Greaney has a degree in international relations and political science. He is the author of The Gray Man series of books. He is also the co-author of Threat Vector, Locked On, and Command Authority with Tom Clancy. After Tom Clancy died in 2013, Greaney continued the Jack Ryan Novel series. These books include Tom Clancy Support and Defend, Tom Clancy Full Force and Effect, and Tom Clancy Commander-in-Chief.