One can believe in many different things. From the most 'noble' to most ridiculous. They beliefs and desires can contradict one another too. The Nazis believed strongly in being supermen riding on the tanks on Russian steppe. They got sobered up only by -40 degrees and hunger in the frost of Stalingrad.. They believed in their squads and their armies, and their nation, they felt strong, they felt elated because they were it, the big thing - it was their ego.
Boys not know what war is, they only know computer games which they play in a cozy room of mom and pop's place. They can be talked into many stupid things by clever or crazy politicians, lawyers or generals. They get ready for war and dream of being heroes but they don't know that war smells of dead corpses, fear and dirt. There are no heroes in the trenches.
How can one prepare for war running with rifles in forests in times of nuclear bombs? One must clearly be hypnotized, spellbound by ideas, beliefs, pride or anger served by the politicians. One must believe one is Japanese, Polish, Russian or American, Christian, Buddhist, Protestant or Muslim. In the fragmentary perception of thought.