Tom Clancy was an American author best known for his military-themed action and espionage thrillers. He wrote several popular series, including the Jack Ryan novels, the Rainbow Six series, and the Net Force series. His works have been adapted into films, television series, and video games. Ryan is a character in many of Clancy's novels, most notably The Hunt for Red October, Patriot Games, Clear and Present Danger, and The Sum of All Fears.