their vehicles. Even after the conquest of Poland, "Blitzkrieg" was not defined on the strategic level. Guderian and von Manstein devised a strategy that entailed what later would be seen as the essence of Blitzkrieg: concentrated panzer divisions performing swift deep penetrations. This strategy was not initially accepted by German High Command. Nevertheless, the final plans for the invasion of France in 1940 hinged on the element of a Schwerpunkt at Sedan, and was assigned to such forces. The great success of this operation led to Blitzkrieg being integrated with strategic planning for the rest of the war. German tanks could carry with them enough fuel and supplies to go almost two hundred kilometers, and enough food to last three to nine days. This relative independence from supply lines proved effective, and allowed them to advance on critical targets much faster and without hesitation. Another factor was the ability of commanders to make strategic decisions in the field and without much consultation with their headquarters, the orders of which were often simply ignored. A prime example is Erwin Rommel's lead-from-the-front approach while commanding 7.Panzer-Division which allowed him a flexible response to the battlefield situation, an instance of the Auftragstaktik (reliance on subordinates to make their own decisions). The effect of German Panzer speed, mobility, and communication shocked the French, and ultimately were the deciding factors in the battle. It overcame their inferiority in armour and armament relative to the main French materiel such as the Char B1 bis. The superior tactical and operational praxis, combined with an appropriate strategic implementation, enabled the Germans to defeat forces superior in armour (both quantitatively and qualitatively) in the battles of 1940, but just as Blitzkrieg became a deliberate military doctrine, in 1941, it ultimately failed on the eastern front, though initially attaining spectacular successes. Before the war, Heinz Guderian had in his Achtung–Panzer! propounded a thorough mechanisation of the German forces. By 1942, increased AFV-production allowed a fuller implementation of this ideal. Now extensive armoured combined arms team could be formed, distinct from a purely infantry or cavalry formation. The panzer divisions integrated tanks with mechanised infantry (riding in halftracks to be protected from small-arms fire while being transported) and self-propelled artillery (howitzers fitted on a tank chassis). This allowed the panzer division to become an independent combat force, in principle able to overcome the problems of attaining a breakthrough against entrenched enemy