There have been many times countries refuse to admit they are at war even though they are. As I have said before war does not have to be fought with bullets it can be fought with pens. Here are a few reasons why the fact they are at war is not made public.

James, does the Law of War Manual apply internationally to other foreign states? Or just to the U.S.?

Everyone. It is also known as the Law of War. It has another name also that is escaping me. It is followed by all large nations and most the small ones. There are some in Africa that don't follow it but still get spanked when they disobey.