Mark Hazzard grew up in a rather cold, heartless family. His father always wanted him to be the best at everything he did. While he did rather well in everything he tried, such as football, he was never good enough in his father's eyes, and Mark's father couldn't tolerate this. All the way through military school, at West Point, this 'tradition' of disappointment continued.
Events came to a head, however, when Mark's father decided that the woman he loved, the woman he was going to marry, also wasn't good enough for a Hazzard man. That was the last straw, and with that Mark got married, quit West Point, and signed up for several tours in Vietnam (as that conflict was raging at the time).
During this tours of duty, Mark put his extensive military skills into play, doing all sorts of tricky missions for the U.S. military. Patrols, seek and destroy missions, and even the occasional stint as a tunnel rat were all a part of Mark's work, and he enjoyed it thoroughly. In fact, his three tours in 'Nam helped to form his vast military theory into impressive practical experience.
Also, Mark assembled a vast array of friends, contacts, and favors to be called in at a future date, as he was about the best there is at what he did, and he often pulled less skilled people's fat out of the proverbial fire. Eventually, though, the war was over, and Mark was shipped home. He couldn't get a job, though, in that nobody would hire vets, so he turned to mercenary work.
At first, Mark simply served as one of many fighting men in a mercenary company, but over time, Mark grew into a leader of such men, and formed his own merc crew. This crew included such rough and tumble fellows as Mal Rossi and Louis 'Treetop' Barrington. This three man crew grew to include lots of other occasional, part-time help, and their reputation grew.
Eventually, however, Mark's marriage went bad, namely because his wife forced him to choose between her and his work, and they eventually got divorced. Her new husband, a slime-ball lawyer named Gordon (last name unrevealed), never got on too well with Mark, always feeling that his wife and step-son liked Hazzard more than they liked him - and, of course, it was true.
As such, Gordon eventually set up Mark to die while on a mission in Iran, hoping he would disappear in that godforsaken desert once and for all. Mark's friends mounted a rescue to save him, and once he got back, Hazzard learned who was behind all of this mess - thanks to some leg-work done by his pal Lincoln Griffin. After dealing with the middle man, one Henri Graymalkin, Mark went after Gordon.
Already wounded from his encounter with Graymalkin, Hazzard was just slow enough that Gordon managed to plug him several times before Mark bore down on him, strangling him with his bare hands. Though he had finally gotten rid of his unknown enemy, the damage was done, and Mark collapsed in a heap of his own blood.
Taken to the hospital immediately, Mark nonetheless was too far gone by the time he'd gotten there, and after a long and arduous operation, Mark was effectively dead, being kept alive only by the hospital's life-saving machinery. Scott, Mark's son, told the doctors to turn the machines off, thinking that Hazzard would want things that way, and as such, the doctors let him die, ending Mark Hazzard's tale.