His case was taken up by the then-president of City College, General Alexander Webb, who wrote to Secretary of War Robert Todd Lincoln on behalf of Greene.

Hazen's opposition rested on the convention (approved by Congress) that black soldiers could only serve in four regiments, two in the cavalry and two in the infantry.

In 1887, only a few years after he enlisted, Greene was unfairly yet dishonorably discharged from the Corps after a series of disputed claims regarding his behavior and character.

He later changed his name and moved to New Orleans, Louisiana to start a new life with a new identity to escape the pain and dishonor brought to him at the hands of the military during Jim Crow.

[7] In 2007, the New York State Assembly's Standing Committee on Veterans’ Affairs paid tribute to Greene's triumphs and challenges with a resolution, "Honoring the Life and Accomplishment of William Hallett Greene, the First Black Graduate of the City University of New York, and Member of the United States Army Signal Corps.