Very interesting thread. What we need to remember regarding German offensives was their doctrine blitz krieg which was the basis for their whole Russian invasion plan. Now, blitz krieg is basically based on pace, pin point attacks and quick break throughs. And here lies the basic reason why they didn't succeed as planned. Blitz krieg doctrine wasn't working due to many, many different factors. Hard weather conditions during autumn and winter, very poor roads, hard terrain, Red Army etc. etc. This is why their offensive got much slower as excepted, supply didn't work as planned and equipment supplied wasn't enough (winter clothing etc.). The plan was indeed to be in Moscow before year end and probably this was stupid mistake by German supreme command blinded by fast victories in Poland and France. That meant that German troops weren't ready to face all those other difficulties in addition to most important of course - the Red Army. So, I do believe (but obviously can't state this as a fact) that harsh winter was one factor among many others to influence German failure in eastern front. For the Red Army it certainly did make it a bit easier to defend and gave little more time to organize themselves and this doesn't take anything away from them.