Alexis de Tocqueville, from Democracy in America Vol. 2, Part 2, Ch. 22 (Gerald Bevan’s Penguin Classics translation):
War does not always surrender democratic nations to military rule but it invariably and immeasurably increases the powers of civil government, into whose hands it almost unavoidably concentrates the control over all men and all things. If it does not lead to tyranny by sudden violence, it leads men gently there by habituation.
All those who wish to destroy freedom within a democratic nation should realize that the most reliable and the most rapid means of achiving it is war. That is the first principle of knowledge.