In this episode, Tim Devine and Jon Gerson argue that the US Army must restore the primacy of mobilization planning to prepare for the growing likelihood of a protracted large-scale war involving the United States. While the Army’s transformation initiatives have emphasized important tactical matters, Devine and Gerson call attention to critical strategic vulnerabilities associated with mobilization—one of the Army’s enduring core functions. They offer insights, identify challenges, and offer recommendations for contemporary leaders and practitioners by analyzing the body of thought on mobilization planning during the interwar period (1919–41) and drawing connections to the present day.