Wars are generally fought by the poor, the uneducated, and the ignorant. Most of them join the military because they see it as the only option to improve their lot, and through advertising, to give their lives "meaning". 

War is invariably fought for the benefit of the wealthy and the military industrial complex.  The government treats their veterans with neglect and contempt once their service is finished.

I wouldn't call them sheep; I feel sorry for them.

A few individuals will serve out of a misguided sense of patriotism even if they do not believe in the cause.