Tom Clancy: Author whose action-packed Cold War novels transformed the thriller genre

The massively bestselling author Tom Clancy was pragmatic about his writing. "People say I write techno-thrillers and Cold War novels," the author of The Hunt For Red October, Patriot Games and Clear and Present Danger said. "I say I write books." However, he wasn't aiming for great art in these books. "I did not write King Lear," he said. "I am not Hemingway, Faulkner or Shakespeare."

But he was a man who changed a genre and few writers do that. His debut, The Hunt For Red October (1984) caused a seismic shift in the thriller genre. Ronald Reagan called the novel "the perfect yarn" for its combination of thrills, global politicking and all the technical knowledge of Soviet submarines and the latest weaponry. The techno-thriller had arrived. So impressive was his grasp of the technology, he claimed, that when in 1986 he met the Navy Secretary, the official demanded: "Who the hell cleared it?"

Thomas Leo Clancy Jr was born in the port city of Baltimore the son of Thomas and Margaret Clancy. He grew up in Baltimore's middle-class Northwood neighborhood.

"I was a little nerdy but a completely normal kid," he said. "Mom and Dad loved each other." He was brought up Roman Catholic, attending the Jesuit-run Loyola Blakefield High in nearby Towson, where students began each class with a prayer. A teacher recalled him as a straight-A student but "unremarkable as a leader or athlete", being "quiet and toward the shy side". But, the teacher added: "He was kind of his own man."

He left high school in 1965 and moved on to Loyola College in Baltimore. At first he studied physics but then switched to English. He was a conservative student, not participating in all the ferment going on around him. He later explained: "Loyola was a working-class college. You had to be rich to be radical." The new music didn't appeal, either: "I was more of a Peter, Paul and Mary kind of guy." (He was a Republican and a Life Member of the National Rifle Association.)

He joined the Reserve Officer's Training Corp (ROTC) but his eyesight let him down and he was obliged to withdraw. He enjoyed reading the manuals and text books on modern technology and warfare, however. He would also read unclassified government documents. This laid the knowledge-base for his high-tech thrillers. He said later: "It's all in the open. You just have to know where to look."

He graduated in 1969 and married his first wife, Wanda, in the same year. They moved to Hartford, Connecticut, where he worked for an insurance company for four years. In 1973 they returned to Maryland and he joined his in-laws' insurance agency. He never lived anywhere but Baltimore and Maryland for the rest of his life.

In 1982 he had an article published in a publication of the Naval Institute on the MX missile system. He was also writing The Hunt For Red October, inspired by a newspaper article about a 1975 mutiny aboard a Soviet destroyer. The novel, about a superpower conflict centred on a renegade Soviet submarine commander, was published in 1984 by the Naval Institute Press for a $5,000 advance. It sold 300,000 hardbacks and 2m paperbacks in two years. Eventually it sold 5m copies.

He followed it in 1986 with Red Storm Rising, written with Larry Bond. A year later, the CIA analyst Jack Ryan, introduced in Red October, returned in Patriot Games. (By 1994 he was President of the United States.) The "official" sequel to Red October came with 1988's The Cardinal of the Kremlin.

Red October was filmed in 1990, starring Sean Connery and with Alec Baldwin as Jack Ryan. Harrison Ford replaced Baldwin in the films of Patriot Games and Clear and Present Danger. Ben Affleck had a shot at playing Jack Ryan and Kenneth Branagh is directing Chris Pine as the latest Jack Ryan for Shadow One, to be released this Christmas. By 1993 Clancy was earning so much money that he could afford to buy his local baseball team, the Baltimore Orioles, with other investors. He remained a part-time owner until his death.

By 1996 he was exploring the link between his novels and video games. In that year he co-founded video game developer Red Storm Entertainment. SSN: Strategies for Submarine Warfare in 1996 was his first novel to link directly to a video game. He did the same thing with Rainbow Six in 1998. By then he was one of those few writers who are brands and like some brands he became a franchise. He worked with other writers and lent his name to a range of video games and board games that had book tie-ins.

The 10 novels in the Net Force series, the eight in the Op-Center series and the Power Play series were all written by others and linked to video games, as were the Ghost Recon, Endwar and HAWX series.

In 1997 it was reported his publishers were paying $50m for world rights to two books and a further $25m for a four-year multimedia deal. He owned a $16m penthouse condo at the Ritz-Carlton in Baltimore in which, it was alleged, he wanted to instal a firing range. He also owned an 80-acre farm overlooking the Chesapeake Bay with a Sherman tank parked on the lawn.

He and his wife separated in 1995. In 1998 he had intended to purchase the Minnesota Vikings but his divorce settlement negotiations prevented him concluding the deal. In the settlement Clancy split his part ownership of the Baltimore Orioles (he was the second-largest shareholder) with her.

His divorce was finalised in early 1999 and in June 1999, aged 53, he married Alexander Marie Llewellyn, 21, the TV journalist daughter of an African-American multi-millionaire. She had been introduced to him the previous year by her second cousin, the four star general and future Secretary of State, Colin Powell.

He wrote or co-wrote or had ghosted 25 novels in all, each one a bestseller. Threat Vector (2012) co-written with Mark Greaney, and his final novel Command Authority, also co-written by Greaney, will be published in December.

He worked five or six hours a day aiming to produce at least five good pages by the evening. He attributed part of his success to his diligence. He once said writers' block was "just an official term for being lazy – and the way to get through it is work."

Peter Guttridge

Thomas Leo Clancy, Jr, author: born Baltimore, Maryland 12 April 1947; married firstly Wanda (divorced 1999), 1999 Alexander Marie Llewellyn; died Baltimore 1 October 2013.