This wasn't anyting like "unexpected" and it wasn't German but German and Soviet invasion. --Taw
Viktor Suworow , (book Ice-Breaker) and book "Der Tag M" (M=Mobilizing Day) proved that the Soviet Army under Stalin was ready to attack. Suworow recently inspected many documents. He was trained in Soviet Army at Suworow Officer School in Kaliningrad and at Officer College Kiev.
Further down in the article it needs to be stated , that the main reason, for bogging down the German army, was weather, the rains and early winter . H. Jonat