Ranks are a symbol you can wear around to brag about your skill in this game.
OK-Here is how it's going to work.
Ranking up is going to depend on the number of enemies you kill, how many blocks you placed, and how many blocks you destroyed. Your rank will be displayed on your shoulder and the side of your helmet.
FIRST RANK-
Recruit
No ignisia
Private
Corporal
Sargeant
Lietunant
Captain
Major
Colonel
General
Before you go "OMG U LEFT BEHIND SO MANY RANKS" I think it would be tiring for the developer to make so many textures for the ranks, plus this is set in the World War I Era. Pleaes support and give me you're feedback (sorry for bad grammar i am not american)

If any ranks were to be added (not that they should):

Player.
Admin.

This would just encourage hackers even more.. Sorry but no.

Erm...

Destroying and placeing blocks to bring up your rank/score? That seems like a good way to encourage pointless block and digging spam.

Basically the general trend here is for people to want the game to be way more complicated than it needs to be.