"The Germans had deceived Stalin by breaching the Molotov-Ribbentrop Pact, and Stalin was pissed off completely. "
After reading "The Chief Culprit" you may want to review that sentence. I am not excusing Hitler at all but according to this source Stalin was about to launch a attack just a few weeks later and Hitler had no choice but to strike first while the Red Army was still building up.
The description of the Finnish-Russian winter war in this book is also very breathtaking, how many Red soldiers were sacrificed to take just one pillbox.