It was Bastiat who observed the trade-off between trade and war. When goods don't cross borders, he said, armies will. Without trade, there is less to lose from the mass destruction that war implies. Countries that trade have a mutual stake in the preservation of open, friendly relations. This is one reason that free commercial activities promote peace, and why protectionism and trade sanctions generate war tensions.
History shows that war is good for government.
In wartime, government gains massive power over society. It is granted a degree of latitude in its use of emergency powers that would not otherwise be permitted. War allows politicians and bureaucrats with a passion for power to use it to the hilt, through taxation, inflation and regimentation. War destroys things and then permits governments to profit from rebuilding them. It drains the private sector of capital and entrepreneurial energy and enriches the parasitical institutions of the State.