When the United States entered the
First World War in April 1917, McAlexander was promoted to
colonel in May and sent to
France to command the
18th Infantry Regiment of the
1st Division. He commanded that regiment during their early tenure in France when it was being trained in tactics by the
French Army. However, he was relieved of command shortly after. It is said that McAlexander was relieved from his command position by General
R. Bullard for profanely refusing to believe that the
French could teach him anything about war. He was sent, instead, to serve with the
Inspector General's staff. McAlexander was assigned to command the newly arrived
38th Infantry Regiment of the
3rd Division, commanded by Major General
Joseph T. Dickman, in May 1918. After the regiment was trained in
trench warfare and modern tactics, it was moved into the line to help bolster the French positions. The French commander, General
Jean de Montdésir, wanted to piecemeal the Americans among his troops, but McAlexander would have none of it, and the 38th wasn't budged until the 3rd Division was given a front of its own, in June, near
Chateau-Thierry. pinning the Croix de Guerre on Brigadier General Ulysses G. McAlexander for his valorous conduct on the Marne river, in July 1918. In July, the
Germans launched an assault against the
Allied line, known as the
Second Battle of the Marne. A three-hour
artillery pounding of the 3rd Division's position announced the beginning of the offensive. In the dark of night, boats ferried the first waves of troops from the
German Seventh Army. In short order, French and American defenses closest to the southern flanks of the river crumbled and were overrun. The enemy was so well established on the 3rd Division's right flank that its position should have been untenable. As a result, McAlexander's 38th was beset from both sides. Apparently, McAlexander had expected just these developments. Without yielding his hold on the Marne embankment, McAlexander refused both flanks so that his regimental front stood like a horseshoe, one battalion forward, one on either side. The Germans attacks were unsuccessful and the regiment held out, maintaining their position. In the much larger
Meuse–Argonne offensive which soon followed, McAlexander's Texans took the fight to the enemy and attributed their success to their leader. After the war, the Texas veterans commissioned a portrait of McAlexander (currently on display in
Austin, Texas) that evokes their admiration of their commander. When the Great War ended on
11 November 1918, McAlexander stayed with the
Allied occupation force in Germany until 1919, when he returned home. ==Post-War==