What role did the doughboys play during WWI?

Doughboy was an informal term for a member of the United States Army or Marine Corps, especially used to refer to members of the American Expeditionary Forces in World War I, but initially used in the Mexican-American War of 1846-48. A popular mass-produced sculpture of the 1920s designed by E. M. Viquesney - the Spirit of the American Doughboy - shows a U. S. soldier in World War I uniform.