evader23,
War level represent your victory's against C3 nations. Each time you win a war against a C3, you move up one war level. As such each war against a C3 nation becomes harder.
At war level 0 you fight a war against a War level 1, winning moves you to war level 1. At war level 1, you fight against a war level 2 C3, moving you to war level 2, etc.
Each war represents a major advancement, in your military capability in prestige. Simcountry doesn't allow us to spam wars by fighting low level C3 nations over and over. Some people think that's good, others hate it. But it is the way it is.
Signed President of DanNation on LU