Blood on the lens.
Okay, when it's, say, Quentin Tarentino, and there is blood spurting everywhere to comical effect, and it gets that much more ridiculous when it breaks the fourth wall and has blood on the lens, it works. It's tongue in cheek. That's fine. Now, lets bring this into a totally serious war drama. Very serious, very dark. I'm reflecting on what being in this situation would actually be like. The movie is very real. It's beyond moving pictures, it's into just experiencing the story. A guy gets shot with an MG, and blood spatters on the lens. I blink. I think to my self, "Oh yes. There is a camera. Because this is just a movie. Those are actors. This didn't actually happen. This is simulating real events, but otherwise, it's all fake. Yawn". Very few things break suspension of disbelief more, while simultaneously adding nothing whatsoever.