Final answer:
The US troops that arrived in Europe during World War I were nicknamed 'doughboys.' They played a significant role in supporting the Allies, and specific units like the Harlem Hellfighters were highly decorated.
Step-by-step explanation:
The nickname given to the US troops as they arrived in Europe during World War I was doughboys. This nickname was chosen because of the white belts that they wore, which were cleaned using pipe clay also referred to as "dough".
The American Expeditionary Force (AEF), under the command of General John J. Pershing, arrived in Europe to support the Allied forces, particularly aiding British and French troops that had been engaged in prolonged trench warfare. While the AEF fought as an independent unit, a specific portion of it, the 369th US Infantry, also known as the Harlem Hellfighters, fought valiantly alongside French troops and were highly decorated for their bravery.