Inspiration from the 'Classic 4 D&D Classes'

[Inyssius]

I always though Eberron's "Five Nations" were based strongly off the four classes (+1).

Ooh, that is clever!

Karrnath (ignoring the undead thing for a minute) is a nation with a strong military tradition, a military draft, and martial law. Its also home to the best military academies in the world. Its archetype is Fighter.

I would add that, in the fine tradition of Fighters everywhere, Karrnath completely botched its Will save. Hence the undead thing (which was mostly a Vol innovation, remember?)