Clancy said his dream had been simply to publish a book, hopefully a good one, so that he would be in the Library of Congress catalog. His dreams were answered many times over, with worldwide sales of his books estimated to exceed 100 million copies.
Alec Baldwin, Ben Affleck and Harrison Ford have all played Jack Ryan on screen and "Jack Ryan: Shadow One" is set to open on Christmas Day, starring Chris Pine as Ryan.
Clancy wasn't always happy about the movie versions of his books. He complained that Ford was too old to play Jack Ryan, and he regretted the lack of creative control, saying: "Giving your book to Hollywood is like turning your daughter over to a pimp."
Clancy started off writing about the Russians, but also told stories of Latin American drug cartels, Irish-British tensions and Islamic terrorism. He wrote nonfiction works on the military and ventured into video games, with a number of best-selling titles.
His recent Jack Ryan novels were collaborations with Mark Greaney, including "Threat Vector" and a release scheduled for December, "Command Authority." As of midday Wednesday, "Command Authority" was No. 35 on Amazon's best-seller list.
Born in Baltimore on April 12, 1947, to a mailman and his wife, Clancy was fascinated by military history as a child. He entered Loyola College as a physics major but switched to English as a sophomore. He later said he wasn't smart enough for the rigors of science, though he clearly mastered it in his fiction.
After school, he worked in an insurance office that had military clients. By the early 1980s he had written a piece about the MX missile system that was published by the Naval Institute. Boredom with his job led him to try novels. He wrote daily and set a goal of five completed pages a day.
Clancy was married twice, to Wanda Thomas and then to Alexandra Marie Llewellyn, and is survived by his wife and five children, according to his publisher. The publisher had no immediate details on funeral arrangements.
AP National Writer Hillel Italie contributed to this story from New York.