This story recounts the role of a black steward in saving the lives of many of his fellow sailors on board the "Oklahoma" at Pearl Harbor, and the role that black men played (and more importantly, the roles they weren't allowed to play) in the navy during the Second World War. Sad to say, though things obviously improved somewhat by 1972, when this story was published it was still pretty unusual to see blacks in a major role in mainstream comic books (it's still pretty rare today).
Glanzman tells the story well, with a great complementary design on the first and last pages to emphasize his point.
Glanzman touched briefly on the creation of this story (and it's dedication to Paul LeBlanc) in his autobiographical sketch in STREETWISE (2001)