A free society is impossible under empire. Even the most just war you can imagine is a disaster for liberty and prosperity. And a perpetual state of war guarantees that liberty will never be achieved. James Madison said it well:
Of the enemies to public liberty war is perhaps, the most dreaded. War is the parent of armies; from them come debts and taxes. Armies, debts and taxes are the instruments for bringing the many under the control of the few. In war, the power of the Executive is extended; its influence multiplied; and all the means of seducing the mind, are added to those of subduing the people. There is also the opportunities of fraud, growing out of war. No nation can preserve its freedom in the midst of continual warfare.