There had been continual difficulty with the all-Negro units sent into Korea, T. R. Fehrenbach explains (in This Kind of War):
The problem is not one of race or color, but of a minority group, anywhere, which has had much of its essential pride as human beings stripped from it. The strongest urge of any minority group, Armenians, French-Canadians, or Untouchables, is to survive. They have no other effective way of fighting.
The old jokes about the military courage of certain minority groups has some basis in fact. Turks joke about the fighting ability of Turkish Christians. The indigenous Christians that Turks know are submerged, wily folk, sharp with money, slyly sticking together against the Moslem world, absolutely uninterested in going out to fight and die for the Turkish State. They see absolutely nothing to be gained by it — nor is there.
A diplomat from Istanbul, several centuries ago, remarked it was odd that Franks in the Western kingdoms were much more like Turks than like Christians. If this Turkish gentleman had visited the medieval ghettos, he might have begun to understand.
Jews in Eastern Europe often went to the gas chambers without a protest, without lifting a hand. The young men of the same human stock raised in Israel are among the toughest, hardiest folk in the world.
[...]
The Columbia professor, and others, discussed practical means of ending the Army’s trouble. They saw only one solution: desegregation.
In front of white men, the sociologists claimed, colored soldiers would feel an urge to prove themselves, and have a chance to develop pride they could never achieve in a segregated unit. They recommended one per squad, or two, no more — because the tendencies of the persecuted are to group together against the world.
[...]
And the United States Army’s combat problem with colored troops was largely ended. Filtered through the white units, they did well. Three weeks after its fiasco on Bloody Ridge, 3/9 performed with excellence.
The social problems, of course, were not solved. A solution to these can be anticipated only when all men look alike, hold the same views, or are so apathetic that it no longer matters.