The night of the 15—16 September the Regiment marched from Bois d'Heiche by way of Remenauville, Limey, Lironville, Noviant and Minorville, to the Bois de Rehanne, where it remained until 20 September. On this date the Regiment marched from Bois de Rehanne, arriving in Toul a little after midnight, where one Battalion was housed in French barracks. The Second and Third Battalions went to Bruley. On 25 September the Regiment entrained at Toul for the Chalons district. After detraining at Chalons the Regiment marched to Neusiment-sur-Coole, where Regimental Headquarters was established. The First Battalion billeted at Coolus; Second at Ecury-sur-Coole, and the Third Battalion at Cernon, with the Machine Gun Company at Compertrix. On 29 September the Division was changed from the reserve of the Group of Armies to the reserve of the Fourth French Army, commanded by Gen. Gouraud. On this date embussing orders for all battalions to a new area were received, transportation overland; and on the following evening the Regiment was transported by camion trains to Camp Piemont, which was reached about daybreak. The camp was already full of French Dragoons and French colored troops, but shelter was finally found for all elements after the troops had been standing around for several hours. During the night 30 September—1 October, while in the camp, a dozen large shrapnel shells struck camp and caused some casualties in the crowded barracks, three killed and Fifteen wounded.

On the night 1—2 October the Regiment went to shell holes on the ridge at Navarie [sic Navarin] Farm, where it was intermittently shelled by 77's during the entire day. The Marine Brigade ahead relieved the French in the sector before Somme-Py. The congestion was bad and roads extremely poor, and this, coupled with indefinite directions, made the march very difficult. The Regiment was commanded by Col. Stuart; the First Battalion by Captain Platner; the Second Battalion by Lt Col. Arnold, and the Third Battalion by Major Denig. The strength was 104 Officers and 3344 men. A reconnaissance of the French front line by the company commanders [l]asted all afternoon, without much success, owing to the vagueness of the French instructions and orders. The First Battalion actually made the relief of French Chasseurs, although the outposts were left in front, and the battalion commander was not notified of their presence. The Second and Third Battalions came up in the middle of the night and were placed in woods nearby with orders to pass through the French line in the morning attack. The Twenty-Third Infantry came up behind the position in support just before dark. "H" hour was 5:50 A.M. 30 October. After five minutes artillery preparation the First Battalion led off, (as per instructions from the French), covering about half the Regimental Sector. The Second Battalion followed, although covering the other half of the attack area. The Third Battalion followed at five hundred Yards. In the First Battalion Companies "C" and "D" were in the front line; "A" and "B" in support; Machine Gun Platoons with "C", "D" and "B" Companies. They encountered a heavy volume of machine gun fire but closed up on the barrage, which was moving at the rate of one hundred meters per four minutes, and followed it to the objective-Medeah Farm-Pylone. The Germans (Saxon troops) stayed by their guns and fought to the end. There were light machine guns in tree tops and many well organized positions and machine-gun emplacements. The Second Battalion advanced with the formation, "F" Company on left of front line, "G" company on right, with "E" and "H" companies in support. "F" Company ran into strong opposition about five hundred meters from the jump-off, illustrating the very small overlap of leading and following battalions, both in front line. After the objective was reached the First Battalion extended over to cover the whole front. The Second Battalion went to the trenches on the ridge in rear. Third Battalion dug in behind the crest. The Boche combed the ridge with 88's and larger, with an observatory and concrete emplacement, and old trenches as special targets.

Considerable artillery had been left in place. The Marines advanced on left and reached the objective practically at the same time as the First Battalion. The Twenty-Third Infantry followed the Ninth at proper distance, closing up on the objective. Snipers in the woods along the Somme-py-Medeah Road and in front of the positions kept hard at work, enfilading all the gaps in the woods. Outposts were thrown well to the front across the ravine, and the Twenty-Third Infantry was ordered to exploit one kilometer ahead. At 6:30 P. M. another advance was ordered and the Second Battalion moved off to follow the Twendy-Third [sic] Infantry at one kilometer. Darkness caught the line after it had advanced about six hundred meters, but the advance continued until it was found that the Twenty-Third was not in front of the right company, though still in touch on the left. The Twenty-Third Infantry had been stopped by serious resistance on the right of the attack area, and had moved to the left toward St. Etienne. The whole front of the Second Battalion of the Ninth Infantry was exposed. The C. O., Twenty-Third Infantry, asked that his right flank be guarded, stating that he was halted in a Boche trench system below St. Etienne-Orfeuil Wood. The Marine Brigade on his left had not advanced.

The Second Battalion of the Ninth Infantry took up position along a narrow gauge railroad and connected up with the French 344th Infantry by patrols. The French had been unable to advance, meeting heavy machine gun fire. "G" and "E" Companies were in the front line; "F" in support. "H" Company had only one platoon left, which was attached to "E" Company. The Third Battalion just crossed the ravine in front of the Medeah Farm Road and took up position in support, the First Battalion remaining along the first day's objective. At daybreak 4 October a stiff counter-attack with heavy artillery preparation was begun on the Second Battalion. There was a heavy mist and stiff fighting. Lt. Col. Arnold discovered that the Boche had infiltrated during the night around the exposed right flank. At 8:10 A. M. he pulled the right company back from the railroad, refusing his right, so that this Company ("G") faced east in the direction of the Boche. Machine-guns were placed to cross-fire and two platoons of "F" Company were brought up around right rear, attacking north and driving the Boche out. They left in great haste, leaving machine-guns and other material, many dead, and leaving also the beginning of an advance system of pits and trenches which had been dug during the night. That afternoon the Regiment was formed up again to follow the Twenty-Third, but the Twenty-Third failed to advance. The Second Battalion could see this and held; but the right companies of the Third and First Battalions swung around to the right, where it was expected that the 346th French would be held up. These two battalions did some heavy fighting, clearing that flank, but had to retire to their original positions when it was found that the Twenty-Third and the French had not advanced. The Second Battalion withdrew on Col. Stuart's order back of Medeah Farm-Pylon Road, following the example of the Twenty-Third Infantry; the Third Battalion being left in front line along the railroad, unsupported on the flanks. The Twenty-Third Infantry was ordered back into position, however, which was again held by daylight, 5 October. Later, the Twenty-Third Infantry was ordered to extend over to the right, connecting with the French, and cover proper sector, as three-quarters of the Brigade attacked area was still held by the Ninth Infantry. On 6 October (the Twenty-Third Infantry had extended over about two-thirds of the way, the 346th French meantime advancing out-posts about five hundred meters. The Second Battalion of the Ninth Infantry moved up from the ridge and filled the gaps between the French and the Twenty-Third Infantry; "F" and "E" in front line; "G" in support. That night the One-Hundred-Forty-First U. S. Infantry came up and spent the night getting into line, mixing in with troops of the Third Brigade. The installation was completed about 8:30 A. M. on the morning of 7 October. Heavy fog saved them from severe losses; being inexperienced troops and their officers having made no reconnaissance, they milled around blindly most of the night, before they could be properly put in place by Ninth Infantry guides. On 8 October the One-Hundred-Forty-First Infantry attempted an advance; but as part of the organization had not received explicit orders for "H" Hour, the attack was not started promptly or in unison, and the advantage of the barrage was lost. The Second Battalion was placed under orders to act as a liaison battalion and connect up the right of the One-Hundred-Forty-First with the French left, remaining about three hundred meters in rear. Dominating fire from the hill which divided the French and American areas not only stopped any advance at the very outset, but seriously disorganized both lines. The liaison battalion went forward and made the attack, advancing about one kilometer in spite of heavy Boche resistance. Elements of the One-Hundred-Forty-First, after once started by this exemple, fought well. It was necessary for the Second Battalion at this point to place a company on the French left, which was faltering under heavy fire. The line was then organized around the point of woods at this point South to a small hill, across it, joining with the French and forming a pocket. "A" company of the One-Hundred-Forty-First and "E" and "F" companies were placed in dense formation along this line with outposts to the north, not the usual formation in depth, which the Boche would expect from the French and from the French Trained Americans. At 5:00 P. M. a heavy counterattack in thick lines was launched from the northeast, directly at the angle. It was made with terrific fire from the edge of the woods and the hill, and as the flanks of the Boche waves came abreast, the Commanding officer Company "A" One-Hundred-Forty-First, led his company forward in counter-attack, mowing the Boche down with walking fire from his Browning rifles. At the same time "G" Company came up across the angle and hill on the run. The Boche, overwhelmed by an attack when he had imagined himself the aggressor, fled, leaving the ground covered with dead and wounded. This juncture proved to be his main center of resistance; but this was his last stand and when he gave up this important point he started his big retreat. At 9:30 P. M. a battalion of the Second Engineers relieved the Second Battalion, which drew back to the old position on the Blanc-Mont Ridge.

The prisoners taken were 1389, including one colonel and sixty officers. Material captured—120 machine-guns, 10 minenwerfers, 20 pieces of artillery. Losses were:

At 7:30 P. M. 9 October the Regiment stood relieved and the battalions marched to camp De La Loude, near Somme-Suippes, for reorganization and rest. On 14 October it marched to Courtisols 0uest via St. Remy and Bussy. Colonel C. W. Stuart was transferred from the Regiment on 20 October, and Col. Robert O. Van Horn, then commanding the Brigade, was assigned to command of the Ninth Infantry in addition to other duty.

On 22 October the Regiment was relieved from its tour of duty with the Fourth French Army to join by marching the First American Army. It left its billets at Courtisols and marched to Valmy, proceeding next day to Camp Cabaud near Les Islettes, where Lt. Col. M. C. Corey was attached for duty with the Ninth Infantry. On 25 October the Regiment, under Lt. Col. Corey, marched via Chemin Romain Tranchee through the Argonne Forest. to the woods just South of Exermont, where the four infantry regiments of the Division were assembled. Regimental Headquarters was at Chaudron Ferme. From this position the Regiment left for the operations of the Meuse-Argonne Battle.