Tribal warriors, citizen infantrymen and levied peasants do their share of fighting, but professional soldiers’ only job is war. They might be mercenaries, but even patriots and faithful men-at-arms need pay (often loot or rewards in conquered lands). In peacetime, soldiers’ tasks include marching, garrisoning and training; in wartime, marching, killing and dying. Common soldiers are often expendable, but generals can’t make history without them.