The Third Division had made its advance into Roncheres Wood on the 29th and was relieved for rest by a brigade of the Thirty-second. The Forty-second and Thirty-second undertook the task of conquering the heights beyond Cierges, the Forty-second capturing Sergy and the Thirty-second capturing Hill 230, both American divisions joining in the pursuit of the enemy to the Vesle, and thus the operation of reducing the salient was finished. Meanwhile the Forty-second was relieved by the Fourth at Chery-Chartreuve, and the Thirty-second by the Twenty-eighth, while the Seventy-seventh Division took up a position on the Vesle. The operations of these divisions on the Vesle were under the Third Corps, Major General Robert L. Bullard, commanding. [Sidenote: The First Army is organized.] [Sidenote: The American sector is extended.] With the reduction of the Marne salient we could look forward to the concentration of our divisions in our own zone. In view of the forthcoming operation against the St. Mihiel salient, which had long been planned as our first offensive action on a large scale, the First Army was organized on August 10 under my personal command. While American units had held different divisional and corps sectors along the western front, there had not been up to this time, for obvious reasons, a distinct American sector; but, in view of the important parts the American forces were now to play, it was necessary to take over a permanent portion of the line. Accordingly, on August 30, the line beginning at Port sur Seille, east of the Moselle and extending to the west through St. Mihiel, thence north to a point opposite Verdun, was placed under my command. The American sector was afterwards extended across the Meuse to the western edge of the Argonne Forest, and included the Second Colonial French, which held the point of the salient, and the Seventeenth French Corps, which occupied the heights above Verdun. [Sidenote: Large troop movements.] The preparation for a complicated operation against the formidable defenses in front of us included the assembling of divisions and of corps and army artillery, transport, aircraft, tanks, ambulances, the location of hospitals, and the molding together of all the elements of a great modern army with its own railheads, supplied directly by our Service of Supply. The concentration for this operation, which was to be a surprise, involved the movement, mostly at night, of approximately 600,000 troops, and required for its success the most careful attention to every detail. [Sidenote: Heavy guns can reach Metz.]