I think one has to keep in mind that fighting a zombie apocalypse would not be a traditional war with "fronts". It's the dead rising EVERYWHERE within your borders, among your populace, and from within the military and law enforcement themselves.
And if infection works like it does in the Walking Dead where everyone is destined to become a zombie no matter HOW you die -- then you face the daily threat of hundreds of thousands of people dying from natural causes everyday, only to become zombies.
And if infection works like it does in the Walking Dead where everyone is destined to become a zombie no matter HOW you die -- then you face the daily threat of hundreds of thousands of people dying from natural causes everyday, only to become zombies.