By the declaration of the armistice on November 11, 1918, the United States had mobilized and deployed millions of soldiers to France helping to break German resistance and end the war. The expansion of American capabilities that contributed to the decision on the Western Front was astounding. The agencies responsible for equipping and supplying forces had increased their operations several hundred-fold as the army expanded from 290,000 to over four million men in 19 months. However, for all its achievements, the American mobilization had been a close run thing. For a time, the obstacles seemed so great that many doubted whether the United States would propel sufficient force overseas to contribute to the war before German victory in Russia or Franco-British exhaustion led to Allied defeat. In the winter of 1917, a crisis arose that led Congress to investigate and the administration to reorganize the War Department. This work examines the targets of the investigations and public distress: the five War Department supply bureaus. The Engineer, Medical, Ordnance, Quartermaster and Signal Departments were the nucleus of the system to support the troops in the field, develop equipment, and purchase necessary items for the Army. These bureaus, which reported to the Secretary of War and assisted his administration of the Army, provided the resources that allowed the Infantry and Artillery to operate in peace and war. Critics at the time pointed to the five supply bureaus as the cause of the War Department’s inability to manage the mobilization effort. What caused the near collapse of the United States’ mobilization program in 1917? In their analyses of the War Department’s supply bureaus, nearly every historian attributes the collapse of the Army’s industrial mobilization effort to some combination of four fatal flaws. They suggest that the bureaus and their chiefs opposed coordination that endangered their autonomy, regularly went around the War Department hierarchy to secure support for their programs, consciously competed with each other for scarce resources, and avoided the most advanced business systems. The emphasis on bureau culpability is misdirected. While incidents related to the four flaws did occur, they were ultimately symptoms of a larger problem. This dissertation will show that the bureaus failed in 1917 because their organizational system was designed for financially accountable and economical purchase in support of a small peacetime force, not operationally efficient high volume procurement at an accelerated tempo for a large force overseas. The real culprit proved to be a major change in American national security strategy that placed more pressure on the organizational structure of the military establishment than its designers had intended it to bear. With the commitment to send a mass army to France, the managerial form of the War Department no longer matched its function. As the scale and scope of responsibilities increased, the supply bureaus did not fall, but were flooded by the requirements of an unprecedented and unanticipated mission. The story of 1917 is one of an administrative system striving to adapt to rapid growth. Within the span of eight months, American plans changed from a strategy of mobile defense of U.S. coasts and territories to the deployment of millions across the ocean to fight a war of attrition in France. Although the bureaus were viable institutions before the war, the existing bureau form proved incompatible with this evolving wartime function. After they had analyzed events in Europe, bureau leaders decided to utilize the existing forms and structures to manage the new functions and strategies. Because it initially appeared that many of the pre-war assumptions about the operating tempo and size of the army would remain valid, it seemed this moderate approach would succeed. But as the realization of the depth and breadth of the commitment to the Allied coalition clarified, the stresses on the existing system increased. Progress in many areas (the bureaus found sources of supply, brought in thousands of new personnel, and adjusted their internal systems) was not enough to retain the confidence of civilian leaders. Overall bureau performance reveals the incompatibility of an existing system with a new mission rather than some conspiracy, general incompetence, or internal power struggle. The United States got more than it bargained for when it declared war on Germany in 1917: it faced an enemy that was far from beaten and faced it with allies who were close to defeat. The amorphous and unpredictable nature of war proved to be the greatest influence on American political economy, not only in 1917, but also for the entire period of the war. By orienting the causes of the crisis away from ignorance and toward the tension that has always existed in America over the resourcing and control of national defense, one can better understand the real challenges facing the army in 1917.