Ranks above Major?

[Sutemi]

I've been playing Steel Panthers II - Modern Battles ever since it got out 14 years ago, but one thing I've never understood:
How does your Major get promoted? Editor shows that there are Lt. Colonel and Colonel, but even if your Major has 10 battle winning streak and dozens of confirmed kills, he never gets promoted! Everone else gets... Why is this? Has anyone ever seen these ranks in the game without using editor?

In all these years this is the only question I have about this game, so I'd be very happy to have some answer. I really wish someone could give me a decent answer :)

[Vesku]

It's been a long time since I've played it so I can't be certain but I believe my commander got promoted beyond Major during 40+ battles of Das Reich in SP WaW.