I just think it's not nice to lie. As far as I remember (and as Serbs themselves say), NATO claims it was never at war against the Serbs because it says it bombed Yugoslavia, and never fought anyone. 
Now this means that either you're a high-rank operative working deep behind enemy lines and conducting intelligence missions (I suppose it happened) or you were just in the peacekeeping forces (to protect the Albanians from the Serbs).