knew the ranges and location of their own strong points. Subsequently, the infantry would counterattack while the attacker's artillery was blind because they were unsure where their own men were. A reserve division was positioned immediately behind the line, if it entered the battle it was commanded by the division whose position had been penetrated. (Mobile defense was also used in World War II.) Responsibilities were reassigned to implement the new tactics: front-line commanders took over reserves ordered into the battle and for flexibility infantry platoons were subdivided into eight man units under a noncom. Field officers who visited headquarters often were invited to speak with Hindenburg, who inquired about their problems and recommendations. At this time he was especially curious about the eight man units, which he regarded as "the greatest evidence of the confidence which we placed in the moral and mental powers of our army, down to its smallest unit." Revised Infantry Field Regulations were published and taught to all ranks, including at a school for division commanders, where they maneuvered a practice division. A monthly periodical informed artillery officers about new developments. In the last months of 1916 the British battering along the Somme produced fewer German casualties. Overall, "In a fierce and obstinate conflict on the Somme, which lasted five months, the enemy pressed us back to a depth of about six miles on a stretch of nearly twenty-five miles" Thirteen new divisions were created by reducing the number of men in infantry battalions, and divisions now had an artillery commander. Every regiment on the western front created an assault unit of storm troopers selected from their fittest and most aggressive men. Lieutenant General Ernst von Höppner was given responsibility for both aerial and antiaircraft forces; the army's vulnerable zeppelins went to the navy. Most cavalry regiments were dismounted and the artillery received their badly needed horses. In October General Philippe Pétain began a series of limited attacks at Verdun, each starting with an intense bombardment coordinated by his artillery commander General Robert Nivelle. Then a double creeping barrage led the infantry into the shattered first German lines, where the attackers stopped to repel counterattacks. With repeated nibbles by mid-December 1916 the French retook all the ground the Germans had paid for so dearly. Nivelle was given command of the French Army. Headquarters routine Hindenburg's day at OHL began at 09:00 when he and Ludendorff