It was not until May 1918, however, that U.S. soldiers played a major role in World War One.
Compared to Austria, Serbia, Germany, France, and other nations, the United States had a relatively brief experience in the war; fighting ceased on November 11, 1918.
The American officers had, however, one thing in common with their counterparts in the armies of the other countries: nobody had even seen a war like this before, and nobody was sure how to fight it.
Many of these officers were experienced, but their experience was irrelevant. They’d been involved in combat in the Philippines and in Cuba as part of the Spanish-American War, and they’d fought Pancho Villa’s Mexican revolutionaries.
The trench warfare in Europe was a different situation. As historian Timothy Nenninger writes,
In World War I, the United States Army entered combat on the Western Front with an ill-defined idea of how to command troops on the battlefield. Although most senior leaders in the American Expeditionary Forces (AEF) had commanded in combat in Cuba, the Philippines, or Mexico, none had experience with large unit, high intensity combat as conducted in France.
Several factors made the ground war in Europe different. First, the size: millions of soldiers, millions of guns, billions of bullets.
The second factor which distinguished World War I from previous conflicts was mechanization. Although machine guns had been used in previous fights, only during WW1 did they become numerous and common. Tanks entered battle for the first time. Other new weapons included airplanes and poison gas.
Advanced and sophisticated levels of industrialization produced weapons capable of killing on a large scale.
A third factor was that the American officers weren’t accustomed to being part of a multinational coalition. Coordination with French and British officers was a new experience.
There are probably other factors which distinguish WW1 from previous conflicts. American officers studied quickly to gain insights into this situation, as Timothy Nenninger notes:
The lack of first-hand experience was mitigated in part by service school education, General Staff analysis and doctrine, and professional writing in service-sponsored journals and books on military art that provided some insight into modem war. But until the summer of 1918 all of the principal elements of the AEF's command process - organizational, doctrinal, technical, and personal - were untested.
Under the command of General John Pershing, the decision was made to keep the AEF together as a unit within the larger multinational coalition. Previously, the alternative route - embedding small groups of Americans inside French and British units, mainly as replacements to “fill the holes” - had been considered.
This decision shaped the American experience of WW1, and in fact created a distinctly American experience of WW1, being different than the French or British experiences.
How and how well the process worked depended on the knowledge, skill, and preparation of commanders and staff officers, and on their interaction. Although the AEF drew on the experience of other armies, how they applied that experience resulted in a distinctly American process of command.
For the U.S. military, WW1 constituted a challenge to develop new forms of command and control. American officers learned to operate in a large, mechanized, multinational context.