Werner Klemperer, yes. And it's directed by Joseph Sargent, who would later direct Shatner and Nimoy in "The Corbomite Maneuver." (And who would go on to direct Colossus: The Forbin Project and The Taking of Pelham One Two Three.)
Its very hard to watch Judgement at Nuremburg
, with both Shatner and Klemperer in what is a very serious drama. Shatner's role isn't much, but Klemperer as one of the judges being tried is actually pretty scary - once you get past the Klink idea in your head.
By the way, those who have ME-TV. should note they will be playing the HOGAN'S pilot next Saturday at 6 pm EDT. Playing one of the prisoners in that pilot is Stewart "Joe Tormolen"/"Hanar" Moss. Moss must have had a small contract with Desilu, as he appears in several early episodes of HH...