John McClane is a detective with the NYPD.
He is not a spy and would look at you with a slightly wrinkled brow and an expression that doubted your humor or your sanity if you suggested it. In his mind he does not deal with spies in any way in his job. He is a cop first, middle, and last thing. He hunts down bad guys and brings them to justice, usually alive. It is what he is good at and the only thing he can imagine doing.
To several different groups of terrorists, foreign and domestic, as well as a couple of would-be Russian dictators, McClane may not be a spy but he is decidedly a major pain on the rear who is either too stupid or too stubborn to stay out of their business. McClane would chuckle in his particular sardonic manner that he was both.
McClane had been a cop in New York City for eleven years before the events at the Nakatomi Plaza in Los Angeles gave him his own brief moment of fame. The Big Apple was his home and the job was something he was good at. Perhaps it was the only thing he was good at, he would say, as his marriage to Holly had fallen apart and she had taken a good job in a career change on the other side of the continent. With her went their two young chilcren, Lucy and Jack.
As the series progresses, the two try to reconcile but then eventually split for good. The children grow up detached from their father only to be forced together again and find out that he has tremendous love for them. He just has a hard time showing it.
McClane also has a tough time following orders. He is considered a maverick or a rogue cop to many of his colleagues and to most of those who had the misfortune to be his boss, he is insubordinate and incorrigible. And this was before his marriage fell apart and he started drinking only to get to "two steps away from becoming a full blown alcoholic" (McClane counters it was just one step). McClane likes doing things his own way. Luckily for him, he has a habit of getting the job done so he has kept his badge despite the indigestion he has generated in upper management.
The leader of the terrorist/gangster band that McClane combatted in the L.A. skyscraper once referred to McClane as a "cowboy", believing he was another John Wayne. McClane jokingly responded that he had always favored Roy Rogers. This led to an inpromptu comment later in the escapade, one that he had used a few times later when the action is about to get extremely rough, "Yippey-Ki-Yay, Motherfu...". It rather fits.