This is coolbert: With regard to the De Puy verity # 8. "Successful defense requires depth and reserves." During the great offenses the Soviets conducted in the latter years of WW2, 1944 and 1945, it was observed that during the offenses, the Soviets did not ignore defensive measures as well. As territory was seized from the retreating Germans, the Soviet army would then consolidate their position by constructing defensive lines in depth in the newly captured territory. To preclude the possibility of successful counter-attack by the Germans. These defenses were constructed to a depth of 50 miles, and this done while the Red Army was on the offensive! These defensive lines consisted of strong points, anti-tank ditches, mine fields, cleared fields of fire, etc. One defensive line would be followed by a second and third, etc, and this all too a depth of once again, 50 miles, and again, all this done while the Soviets were on the offensive!