HoldenMcGroin is correct...integration of the U.S. Armed Forces did not happen until post WWII.
If you will read your USMC History, you will find out how many African-Americans served on Iwo Jima, how they served, how many were wounded, how many died on Iwo Jima, and how many African-Americans were awarded medals for Valor on Iwo Jima, and why.
I read, Flags of Our Fathers,and I saw the film. In my opinion, the film followed the book. If Mr. Lee has a problem with the absence of
African-Americans not being represented in the film, "Flags of Our Fathers", he should probably take issue with the book's author, Mr. James Bradley, rather than the film's Producer, Mr. Clint Eastwood.
This just my opinion.
Semper Fidelis!