need help with movie title

[catseye]

I have actually been trying to post this question on the imdb board for Where Eagles Dare but I can't get in. I recently saw it again and it reminded me of another movie that I can't really remember much about other than I enjoyed it. The only thing I can remember about it, and this memory is old and mixed up, is that it is about some sort of allied mission and they capture a Nazi officer but he turns out to be a Jewish actor with a blond wig impersonating some important Nazi officer so he has a lot of power. He has just been sort of "winging it" so he can stay alive, just playing his part So he becomes part of the allied mission. That's all I can remember! I can't even remember any of the actors in it, but I think they were big names. Please help, any nazi spy movie buffs out there, somebody must know what movie I'm talking about. Thanks!