The Book of Merlyn is White's attempt to Solve War, and since he was writing at the beginning of World War II I can see the desperate appeal of Solving War... but the strength and the tragedy of The Once and Future King is that it tries so hard to Solve War and fails. No one has figured it out yet, not Arthur, not Merlin, not Woodrow Wilson at the Paris peace conference, and that (says White, staring bleakly at the daily newspaper) is why we are doing this yet again.

...But I can see why that wasn't an emotionally satisfying ending for him in that moment and he WANTED to go on and Solve War. God knows I would like to be able to Solve Trump right now.