The racial tensions within the army
This film is just as good as Platoon or Full Metal Jacket, but it did not get the same level of credit as it was released just after those two.
One of the things Hamburger Hill focuses on is how the racial tensions were between black and white soldiers. It could only take one bigoted remark to trigger off a flare up. From the late 1960s onwards, this was a serious issue that affected the morale of the army.