Sir Laurence Olivier, who had difficulties remembering his lines, initially (very politely) refused to work with dialogue boards. Only after the dialogue coach asked his co-star Maximilian Schell to tell him that all actors worked with boards, he agreed to do so.
Maximilian Schell, presuming there were hidden microphones in the Russian hotel rooms, preceded every rehearsal with a preamble that the following was a rehearsal and not espionage.
Russian (Soviet) soldiers were used as extras.
On a day when the outside temperature was only minus eighteen degrees, Maximilian Schell remarked "it is warm today".