A very important movie, as another one by him, Hiroshima mon amour. Nuit et brouillard is a very hard movie, very strong. I think it is one of the first movies treating this terrible subject, giving the chance to think about all this, all the horror and all the consequences. Thanks to remind us about this movie, I think I will see it again.
I also saw "Hiroshima Mon Amour" around the same time in 1987, and also remember it being very powerful. FWIW.
Yes, very powerful. Extremely interesting about how we perceive the others, about racism, about the war, about compassion. I remember one sentence that always comes during the movie:
tu n'as rien vu a Hiroshima. (You didn't see anything at Hiroshima.) We can look Hiroshima but we were not there. Museums can not express the horror, films can not express the total horror. But for us, that we were not at Hiroshima or in the concentrations camps, films and human contact, love, fraternity, are one way that we have to try to understand. I like very much Alain Renais. He is not an easy director, he is also very poetic. Another very important movie by him is
La guerre est finie. (The war is finished). But the war is not finished, in fact. The war is something that is always there, the war, the sufferance, the intolerance, the fight against it. Spanish people should see again this movie.

Today, more than before, those 3 movies are very actual. Like if Time is coming back. Strange.