“Everything in war is very simple, but the simplest thing is difficult.” Thus remarked the renowned Prussian strategist Carl von Clausewitz in his seminal work On War. Casting a fleeting look at the respective strength of arms, experience, and professionalism of the Red Army and the Wehrmacht on the eve of Operation Barbarossa, one might be forgiven for thinking that on this occasion the ensuing war would indeed be very simple, even easy. Certainly many at the time thought so, yet deficient German planning and dogged Soviet resistance proved the virtue of Clausewitz's maxim. Indeed, from its very inception Operation Barbarossa was a problematic enterprise based on poor intelligence and an erroneous understanding of warfare in eastern Europe. Hitler's Ostheer (Eastern army) soon encountered problems, and a drastic cycle of improvisation forced a radicalization in tactical methods and strategic choices. At the tactical level, radicalization manifested itself in the increasingly arduous experience of warfare as dangerous materiel shortages, unceasing operational demands, and unprecedented losses overwhelmed units. At the strategic level, the radicalization stemmed from the failure of German plans to rapidly end Soviet resistance, leading to the command crisis over how best to continue the war. Certainly Hitler's war in the east was in many ways unique, but in military terms the Wehrmacht's problems were prefaced by past campaigns.

In his biography of Charles XII of Sweden, Voltaire noted that “there is no ruler who, in reading the life of Charles XII, should not be cured of the folly of conquest.”