Final answer:
The "Harlem Hellfighters" - the African American regiment known as the 369th Infantry - is credited with saving half of the American army during World War I.
Step-by-step explanation:
The story that gives someone credit for saving half of the American army refers to the heroism of the African-American regiment known as the "Harlem Hellfighters." This regiment, officially known as the 369th Infantry, fought alongside the French during World War I and suffered high casualties. They earned the respect of the French, who awarded the entire regiment the Croix de Guerre, a high honor usually reserved for individual acts of heroism.