Liberty requires that the citizenry be ready to defend it, sometimes by armed force. In reality, when facing danger, most citizens rush for help to a certain agency, usually a government one. “We shall cede some of our liberties if you promise to protect us.” That’s how terrorists win.
How about wars, then? I believe prolonged wars lead to an unpleasant assimilation: the more decent party slowly acquires the ugliness of the less decent one. Had WWII lasted for ten more years, Britain would have resembled one of the constantly warring empires from 1984. Churchill, for all his greatness, had some character flaws that under different circumstances would have made him a true dictator. Not to mention that WWII made large-scale nationalization in the UK both politically acceptable and technically easy to achieve.