In part:
Quote Originally Posted by ganulv View Post
Am I right to assume that some of the (indeed, deeply shocking) loss of life was of a piece with pre-War Stalinist political purging, economic reorganization, and social engineering?
The scale of the purges is incredible:
The purge of the .... removed three of five marshals (then equivalent to five-star generals), 13 of 15 army commanders (then equivalent to three- and four-star generals), eight of nine admirals (the purge fell heavily on the Navy, who were suspected of exploiting their opportunities for foreign contacts),50 of 57 army corps commanders, 154 out of 186 division commanders, 16 of 16 army commissars, and 25 of 28 army corps commissars.


At first it was thought 25-50% of Red Army officers were purged, it is now known to be 3.7-7.7%. Previously, the size of the Red Army officer corps was underestimated, and it was overlooked that most of those purged were merely expelled from the Party. Thirty percent of officers purged in 1937-9 were allowed to return to service
From:http://http://en.wikipedia.org/wiki/Great_Purge

My recollection is that the German military closely followed the Stalin era purges of the Red Army, which reduced its effectiveness, but as the Japanese learnt @ Khalkhin Gol they could still fight. See:http://en.wikipedia.org/wiki/Battles_of_Khalkhin_Gol

After a disasterous start in the 1939 war with Finland, the Red Army gathered up its might and defeated the Finns. I assume the Germans altered their assessments.