Perhaps it is the intensity of the fight that makes the difference. Everything that a nation has is put into the struggle. New powers are developed, new forces are let loose, new capacities are discovered and exploited, and these have a permanent effect. Beyond either victory or defeat they go on working; it becomes impossible for the warring nation to go back to its prewar status simply because the effort of fighting the war has destroyed that status forever.
The classic example of this is, of course, that hardy perennial of the modern book lists, the American Civil War, and Allan Nevins examines the process in an excellent new book, The War for the Union . He subtitles his book “The Improvised War,” and he is chiefly concerned here with how the improvisation took place and what it finally led to.