But it's a new world. Economy has changed. We now deal with each other at so intense a pitch that national economies are gone. The planet is now largely functioning as one economic system. Economic systems long for stability.
War has a nasty way of destroying capital.
Military has changed. It no longer takes months for kings, prime ministers or presidents to call up troops. Armadas do not gather for weeks to set sail. There are no more Normandy invasions. Instead, standing armies keep giant airplanes and self-guided missiles ready to strike anywhere in minutes.