[Mass Combat] PLAUSIBLE army diversity in settings

[vicky_molokh]

Greetings, all!

As part of [re]designing a setting, I'm aiming for making the [para]militaries different from each other. The problem is making sure the differences are at least plausible - traditions, civilian practices and the like can only account for so much weirdness. What ways can be used to plausibly avoid the armies of the world from picking a perfect mix and sticking to it, and make it reasonable for different organizations to stick to very different doctrines. Preferably with bits of 'ethnic badass' units and tactics.

This was a crude attempt of a similar discussion (more specific to the setting, not as generic as this one).

Thanks in advance!