At the moment the war system favors those who have more military than their opponents, two or three attacks during the first round can cripple an opponent for an entire war.
Therefor I propose that a nation has the ability to "conscript" a portion of their population into "soldiers".
Ideally at 20-30% of their entire population can be conscripted and in order to pay for this a nation would have to sacrifice the infrastructure (possibly) or some other means to balance it.
I simply suggest this as it's become apparent in the latest war that even with multiple targets, if you outnumber them with military chances are the war is already won, it'd be nice to have some method to fight back even if you're outnumbered. Sitting doing nothing while someone pounds your nation isn't fun and I can pretty much guarantee that you'd lose players each time a war breaks out because they're unable to fight back.