Not really an answer, but Western sources are already pretty positive about the Soviet defense there. I’d be surprised if communist sources differed much.

This is not an answer to your question, simply because I do not have one. I just want to recommend checking out the works of Vasilij Grossman. I’m not sure how much of a true communist he was at heart, if at all, but he has a few books on the war from the Russian perspective. Considering the state of censorship in that era in USSR, I would believe his works align fairly well with official communist standpoints.

He has one book about Stalingrad (For a Just Cause), but I think that’s fiction set in a historical context. Don’t quote me on that, though, I haven’t read it myself.

I’m not 100% sure about the English title of the book by him that I have read, but I think it was “A Writer at War”. He produced it a few years after the war, compiling his notes and experiences into a proper book. It’s a really interesting read, and I highly recommend it.