"Take a look at a castle. Any castle. Now break down the key elements that make it a castle. They haven't changed in a thousand years. 1: Location. A site on high ground that commands the territory as far as the eye can see. 2: Protection. Big walls, walls strong enough to withstand a frontal attack. 3: A garrison. Men who are trained and willing to kill. 4: A flag. You tell your men you are soldiers and that's your flag. You tell them nobody takes our flag. And you raise that flag so it flies high where everyone can see it. Now you've got yourself a castle."
— Lt. Gen. Eugene Irwin, The Last Castle