Chainmail,
We used to have 2 terms. Careerman described a man whose career was in the military. Lifer was a careerman who was an a-hole about it.
Back in the day (my day at least) we had three terms:
Career Soldier, more or less described previously.
Lifer, someone who stayed in because it was relatively easy compared to civilian life: you got three slops and a flop, you had someone to tell you what to do and you were ok as long as you did what you were told, you didn’t have to think all that much, just hit the marks that were given you.
Lifer Pig, someone who enjoyed being able to bully, lord it over, etc those with less authority or rank.
Since then, in my own mind, I’ve added the category of Professional, the Duty-Honor-Country type who’s willing to put it on the line for Duty-Honor-Country.