Levon Cade is a former Marine.
That really does not tell anyone much and that is because what there might be to tell is classified and Cade would almost certainly not talk about it even if it was not. So, despite the fact that his official record back in Washington is fairly thick with all he has done over his adult life, most of it is highly redacted. Reading it would only let a person know he has done one impressive amount of things covertly on behalf of his country and not let the reader know anything of what that was.
When we first meet him, this son of the hill country of northern Alabama is back home working as a carpenter. This is not what he would have wanted to be doing but his wife passed away not too long before from cancer and he has a daughter nearing her teens to take care of. At least he would if his father-in-law, a very successful surgeon and powerful civic leader, had not blamed him for that woman's passing and was not fighting with everything he had to keep the young girl away from her father. It takes every cent Cade has to fight for the visitation he has. Which is why all the first adventures we read about came to be - money, or more specifically the need of it to fight for his daughter.
Cade can be a very, very violent man. The key word there is 'can' because Cade does not go looking for trouble. He also does not step aside when it approaches. He will not back down because he has learned that just give the trouble fuel. So when problems pop up and he does not move away, things tend to go badly for the trouble. Of course, being human, Cade takes more than his share of damage but as is shown over and over, he gives a lot more than he takes.