His regiment was mobilized on 23 June 1916 and served along the Mexican border. After the United States commenced hostilities with Germany in April 1917, Krueger was assigned to the 84th Infantry Division as its Assistant Chief of Staff G-3 (Operations), and then its chief of staff. In February 1918, he was sent to Langres to attend the American Expeditionary Force General Staff School, and in October 1918, he became Chief of Staff of the Tank Corps.