Having gone all the way to Moscow, with the Tsar and his army retreating before him, Napoleon is supposed to have exclaimed this when he got word that the city around him was burning, set alight by the Russians themselves:
"What an astonishing decision! This is one that couldn't be calculated!"
I read the story of Napoleon's great army in a book Episodes from History when I was a little kid, and ever since I've been using that sort of half-detached line - "This is one that couldn't be calculated!" as a stock comment either, in irony, for things that you could obviously see coming long before they happened, or for when something totally unexpected does happen.