The most thorough--and recent--study of this event is: The Buffalo Soldier Tragedy of 1877, by Paul H. Carlson (Texas A&M University Press, College Station,Texas, 2003)

I am not sure, but I think Capt. Charles King coined the term "Nolan's Lost N****r Expedition"--although my memory may be faulty and the culprit was a period journalist.

(posting modified by forum moderator to exclude the "N" word)