Do people lack compassion and common sense?

From a macro perspective it can probably be defended to participate in some war activities. But from a micro perspective, the human perspective, how can it ever be allowed?

Innocent people are always injured and killed in a war, and children too. Unless you believe in reincarnation, how can anyone have the right to decide on such things?

To prevent war is necessary, but participate in a war in some forreign country, how can that ever be the right thing to do?