In an interview on NPR about his upcoming movie, set in Vietnam during the war, when it was mentioned, "viewers get the sense the black troops might turn on the white troops," Spike Lee responds, "All the black Vietnam vets who saw the film — four different screenings — confirmed that. It's not something that's been talked about. But the black soldiers were about to set it off. They were going to start firing guns — and it wasn't going to be at the Viet Cong. We're fighting people who've done nothing against us. And in the middle of all this, we hear that Dr. Martin Luther King has been assassinated. And on top of that, their black brothers and sisters are burning stuff to the ground. In over 120 cities, America was in flames."
I've heard it explained as mostly behind the lines brawls between drunk soldiers, but nothing like the near revolt Lee describes. Is he sensationalizing to promote his film, or is this true? If that really almost happened, how did our military prevent it and keep all the soldiers on the same side, trusting one another with their lives, sacrificing for one another, and following orders?
While modern scholarship do not fully support the possibility of a widespread revolt among African American troops in South Vietnam after the assassination of Dr. Martin Luther King, Jr., there was undoubtedly an increase in racial tension, in particularly in bases and installations, which occasionally resulted in race motivated violence. The tension that existed between white and black soldiers was not only present in South Vietnam, but also in the United States, Germany, Canada, and other locations where American troops were stationed.
First, I feel like it does need to point out that Spike Lee is drawing quite generalized conclusions from the experience of a few veterans. The experience of African American soldiers during the Vietnam War era was never one, monolith experience. What motivated African American soldiers, both volunteers and draftees, varied and while there certainly were resentment to be sent to fight for a nation who actively suppressed your civil rights, there were also African American soldiers who saw a career in the armed forces as a viable and even good job. This diversity in thought is made even more clear among those who were active in black organizations while they were in the US armed forces (both state side and abroad). There were organizations that were more focused on political and cultural education to those who were oriented towards revolutionary action of the kind that Lee mentions. This is reflective of the plurality of black activism. The US military leadership actively tried to suppress any black radicalism within their ranks and managed to somewhat constrain it to the point of immobilization by 1973.
It is important, therefore, to consider the aftermath of the assassination of Dr. King in 1968. While there were white soldiers who were equally shocked and saddened by the news coming from the United States, there were also white soldiers who openly celebrated the murder. In Cam Ranh Bay, a Confederate flag was hoisted in celebration and white men donned improvised Klu Klux Klan robes, burned a cross, and paraded around the base. This wouldn't be the first time, as James E. Westheider points out, as crosses were burnt in both 1969 and 1970. Furthermore, the Confederate flag was openly displayed by white troops throughout the war, something that African Americans rightly despised. While white soldiers flew the Confederate flag, black symbols (such as the "Black Is Beautiful" poster) were actively suppressed.
However, as you mention in your post, these events largely took place behind the lines and not at the frontline. While there was racial tension at the frontline, it never took the form that it did in bases or installations further back in the line. Units that saw active combat had comparatively little racial issues due to, as Westheider so succinctly puts it, "combat and the threat of death being the great equalizers". As a 9th Infantry Division soldier put it, "You know when I am out in the bush carrying a grenade launcher, no white man is going to call me n----r."
Yet this should not in any way discount the experience of the racism that African American soldiers experienced throughout their time in the US armed forces. Institutional racism was very, very present during the Vietnam War and although the US armed forces did introduce reforms to combat it, the results came a bit too late for it to have any impact for those deployed in South Vietnam.
Sources:
In my opinion, Fighting on Two Fronts: African Americans and the Vietnam War by James. E. Westheider (New York University Press, 1997), is the best book for the reader who wants an overview into the African American experience during the war. It not only focuses on South Vietnam, as the title implies, but also looks at the experiences of African American soldiers in the United States and Germany.