Sort of like Schrodinger's cat...

Tricky people Germans. Have they or haven't they? It's the sort of thing most people like to do during wartime; use demolition charges to blow things up. Almost everyone does it. But you just don't know with the Germans. Sometimes they do, sometimes they don't. It's not a question of being flippant or careless it's a question of making things difficult for the enemy. And that's what war is all about in some ways. If there are demolition charges in place that would force the enemy into one course of action - if there are no demolition charges that would force the enemy into another course of action. The charges are both there and not there until you get to the bridge. Sort of like Schrodinger's cat but with steel and explosives instead of felines and cardboard.

By the way Schrodinger was an Austrian scientist who didn't like Nazis.