War happens.
It’s a truly terrible, horrible thing that happens. But that is not something that the common man wants or has control over. Not the common man but the government man that declares war. War over oil, war over territory, war over culture.
For any desire for power they want to fulfill under the name of the country and its people, the government officials that are meant to represent the people they swear to serve and protect, draft them into the military so that they can serve and die as mere pawns in their game of chess.

When a government declares war on the enemy, it is because of political conflicts and clashes, and in that opposition, with haste they tell their own people that the “other side” always seeks out to terrorize and threaten their very way of life simply by being different, feeding their minds with images of a mockery and bastardization of their ideals, morals, and culture; this is how they get man to ostracize their own neighbors, even when they are hurt, even when they disagree with the government of the other side.
This is the poison that the government feeds man, and that is the hateful mindset they are only equipped with when they are sent out to war. It comes to a point where one is deaf to the atrocities of their own country, blindly believing their cause, this poison, for they are already succumbing to ignorance.
But even with all of that, man is still the common man, and they know that the enemies on the other side are common men just like them, drafted by the government. Even on opposite sides, they both fully well know that they are a part of the same coin. So do the people on either side really want to bring bloodshed upon the other?

It is unlikely that this is what every man on the field truly believes. But they know well the other side has succumbed to the poison, believing them to be demons and terrorists all the same.
And when all said is done, both sides of the coin will all fall down the same, for it is only the higher powers up afar in their cozy mansions that will win in the end.