Ludendorff, the master tactician, was facing a new problem. That once dependable German machine was not responding with the alacrity, the team-play, and the bravery which had been his dependence in all his plans. He had to consider, in view of the situation that was now developing, whether or not the Saint-Mihiel salient was worth holding at a sacrifice of men. He knew that we were to attack in force; he knew that in an offensive a new army is bound to suffer from dispersion and from confusion in its transport arrangements. If he allowed us to strike into the air, he could depend upon the mires of the plain of the Woëvre to impede us while the defenses of Metz would further stay our advance, with the result that his reserves, released from Saint-Mihiel, might safely be sent to resist the pressure on the Anglo-French front, either in holding the Hindenburg line or in the arduous and necessarily deliberate business of covering his withdrawal to a new and shorter line of defense based on the Meuse River. The German war machine, which had been tied for four years to its depots and other semi-permanent arrangements for trench warfare, could not move at short notice. A generalization might consider the war on the Western Front as two great battles and one prolonged siege. For the first six weeks there had been the "war of movement," as the French called it, until the Germans, beaten back from the Marne, had formed the old trench line. Throughout the four years of siege warfare that had ensued, the object of every important offensive, Allied and German, had been a return to the "war of movement." After a breach had been made in the fortifications, the attacking army would make the most of the momentum of success in rapid advances and maneuvers, throw the enemy's units into confusion, and, through the disruption of the delicate web of communications by which he controlled their movements for cohesive effort, precipitate a disaster. The long preparations which had preceded the offensives of 1915, 1916, and 1917 had always given the enemy ample warning of what to expect. He had met concentrations for attack with concentrations for defense. The sector where the issue was joined became a settled area of violent siege operations into which either side poured its fresh divisions as into a funnel. Succeeding offensives, in realization of the limitations of a narrower sector,--which only left the advance in a V with flanks exposed,--had broadened their fronts of attack; but none had been broad enough to permit of vital tactical surprises after the initial onset. The attrition of the man-power of the offensive force had so kept pace with that of the defensive that the offensive had never had sufficient reserves to force a decision when the reserves of the defensive were approaching exhaustion. Moreover, the Allies had never had sufficient preponderance of men, ordnance, and munitions to warrant undertaking