One of the benefits of establishing the most comprehensive databases that extends back thousands of years is the fact you can run studies and correlate trends. What jumps out at you from the data concerning war is very simplistic – war does not unfold when everyone is fat and happy. Turn the economy down and war rises just as we are seeing wide-scale civil unrest. These trends go hand in hand.
Government often NEEDS war because when the people get angry, they go after government. In self-defense, government ALWAYS needs to blame some other country or group.