I was in the Navy during the Vietnam war, and I don't recall much self-segregation. People in the Navy tended to hang out with men they worked with, and aboard my ship blacks were pretty evently distributed among the various divisions -- except for the Operations and Intelligence Division, where I worked. For some reason, we had no blacks assigned to us. But the men -- black and white -- who served in the other divisions -- Deck, Engineering, Gunnery, etc. -- seemed to get along well ashore.

Friends of mine who served in the Army in Vietnam reported an entirely different situation, especially in the later years of the war. According to them, blacks segregated themselves and were very hostile towards whites and Hispanics. A lot of racial assaults took place during this period. My friends said that it was worse in the support units, not quite so bad in the line units.

I don't know anyone who served in the Air Force in Vietnam, so I don't know what their racial situation was.

Later, when I joined the Coast Guard, I encountered no self-segregation at all. Of course, the Coast Guard is the smallest of the armed forces, and is almost like a family in some ways.