While the major powers struggled for mastery along the Western Front during the first three years of the Great War, the United States had a unique opportunity to ready itself for possible belligerency. Yet, when Congress declared war in April 1917, the entire country, and especially the U.S. Army, was unprepared for war in Europe. For a host of reasons, the Army made few significant changes to its official combat doctrine, despite accurate reports of fighting in Europe that warned of practically revolutionary changes on the battlefield. After the American declaration of war, the Army had a second chance to prepare itself for combat on the Western Front because no American unit did any significant fighting for the next thirteen months. Although the U.S. Army and the AEF made enormous strides before the armistice in November 1918, particularly in organization and logistics, many senior leaders resisted making the intellectual adjustments necessary to effect the kind of fundamental doctrinal changes demanded by the modern battlefields in France. Senior leaders did modify official combat doctrine – but they did so belatedly, slowly, and incompletely.

The U.S. Army, 1914–1917

The extent of the U.S. Army's lack of preparedness for the First World War would come as no surprise to those familiar with the basic American attitudes toward military forces and budgets from 1800 to 1917.