1 September saw the regiment moved by truck from the Vosges Mountains to Nancy and then into reserve for the Saint-Mihiel attack of 12-16 September. This surprise attack was so successful that the 35th Division was not used, and it was soon headed for the greatest American battle of the war. 25 September found the 137th Infantry in position facing Vauquois Hill, an impregnable natural fortress the Germans had held over four years. In the Meuse-Argonne Offensive, a 6-hour barrage was launched on this hill and was taken by the Kansas soldiers in their first attempt on 26 September, and their trial by fire began; an ordeal that was to last six days and six nights, with little or no food, only snatches of sleep, and an uninterrupted rain of shells, gas, and bullets from infantry, artillery and warplanes. The 137th Infantry took every objective assigned it, but in the taking suffered casualties of nearly 1,300 men out of the 2,800 combatants engaged; 46%. The regiment was relieved by the 1st Infantry Division on 1 October 1918, and after resting in the rear for 10 days, the regiment moved to Verdun and remained in the fighting until 4 November. They were in the thick of fighting until 9 November when they were relieved. The Armistice of 11 November 1918 finally stopped the fighting, after which the regiment returned to Kansas, where it demobilized at Camp Funston between 9 and 11 May 1919.