I enjoyed the movie, but when I first saw the trailer I thought Jason Isaacs would be playing Marshal Rokossovsky instead of Zhukov. He looks more like the form

I enjoyed the movie, but when I first saw the trailer I thought Jason Isaacs would be playing Marshal Rokossovsky instead of Zhukov. He looks more like the former than the latter. But I don't think Rokossovsky was heavily involved in Kremlin politics at the time (or ever, other than getting bones broken while in captivity during the Great Purge).