I would like to identify a probable 70's movie about a captured allied soldier. The German captors set up a fake hospital away from the city, complete with ingenious and very convincing details. The prisoner keeps some important military secret his captors covet, and when he wakes up he is told that the war is over and the Germans won, that he was hurt and has amnesia, and that he should rest and be released when fully recovered. Meanwhile they try to get him to reveal the secret claiming it no longer matters since the war is over. The soldier almost falls for it, but in the end he notices a small but troublesome paper cut hidden in a fold in his finger, and therefore not found when his captors painstakingly inspected his body for recent wounds. The cut is obviously recent and he remembers how it came about, thus proving the whole thing is a charade and the secret is not revealed.
UPDATE: Solved, it's "36 Hours".