I can only imagine how casualties are hidden... for a start they probably retain the information whatever they can. Eventually they have to communicate to their families but probably they tell them that it is a matter of "national security" and that the "hero" died for the country in a very secretive operation and not to communicate publicly... who knows, even they may sign them a confidentiality paper...
I wish people were far more skeptical of governments that for a century is routinely sending hundreds of thousands youngsters thousands of miles away for "defense".