Tom Clancy: Without Remorse

Without Remorse is an attempt by the author to explain the emergence of his other main character (the main character is Jack Ryan, but there is also a CIA operational executive called John Clark), the man who carried out a number of field operations including execution and even spying (with mention in many books such Clear and Present Danger, Sum of all Fears, Debt of Honor, Executive Orders, Rainbow Six, Bear and the Dragon). The movie is set in 1971, in the middle of the Vietnam War.
Most people know of the Vietnam War as a major disaster where the US lost 54,000 soldiers and where it had to beat a humiliating retreat, but the Vietnam War was also the one where the US military developed its special operations forces to a major extent, including the SEAL teams, trained in extraction, working behind enemy lines, underwater jobs, and enemy executions. The novel tells the story of one extraction, as well as the story of a former SEAL whose girl-fried was killed by drug dealers in a macabre way, and his revenge using all his abilities. Without Remorse refers to this fightback and the cold blooded way in which this former special operations man targets drug dealers without any pity.
In the Vietnam War, many Americans Prisoners of War were kept in bad Prisoner of War camps, ill-treated and many times not reported to the Red Cross. They were interrogated and treated very badly. It was a mission for the Special Operations team to try and extract them, but this was also a political mission, needing permissions from the political leadership, with the risk of such operations being revealed. In fact, a previous such operation had been a failure, and given that there were also peace talks ongoing, the State department did not want to agree to such operations due to the fear of the peace talks collapsing.
The hero of this book, John Kelly was a former SEAL and a hero who had taken part in many operations in Vietnam, being a part of the SOG (Special Operations Group). He is now retired, and is in pain, having lost his wife in a road accident. At this point, he meets up with Pam, who has escaped from the torture of a brutal drug dealers network where she was one of the couriers as well as the comfort women for the drug dealers. However, as she is getting cured, in an exaggerated sense of bravado, Kelly exposes her to danger and she is taken from him (while he is shot to a near death state). She is soon killed by them in a particularly brutal way.
As Kelly recovers, he learns, and and that is when he vows to use his specialities to hunt down her killers (in a pretty well written part, the nurse and his future wife, Sandy, sees death in his face, a controlled and determined death). He starts his mission of recovery while the police case does not go anywhere. He is also approached by the military for another rescue mission in Vietnam because of his knowledge of the location. For this mission training, he is given a CIA moniker, John Clark, and starts training with the military.
He also starts dealing with the drug dealers, first finding the dealer who started Pam onto the life of prostitution, killing him, and then starting to kill more of them after interrogating them to find out about the main drug dealers, no mercy involved. In fact, were it not for the fact that Clancy was writing about death and murder, those are very well-written and detailed sections. He also rescues a girl and hands her to Sandy Toole (the nurse who helped him), thus making it clear to Sandy that in fact John is doing the drug dealer killing that is making the newspapers. When this girl is also killed after being rescued, he suspects that the police is also infiltrated and is more convinced that the drug dealers need to be killed. There is a very detailed section on the interrogation of one of the capture drug dealers using a standard compression and decompression chamber.
He rescues more girls, and in a stand off, kills the drug dealers behind the killings of Pam. By now the police have identified who could be behind this, although they have no evidence against him. In his rescue mission, he fails somewhat because the rescue mission has been leaked, but he kills the brutal Camp Commander and captures a Soviet air officer who was interrogating the prisoners. This is used to transfer the prisoners to a safe location so that they would not be killed.
In the end, Kelly gives up his identify and becomes a full fledged CIA person by faking a boating accident as he is being pursued by the police and the Coast Guard.