Calling 20,000 soldiers 20,000 troops is a distancing strategy, a euphemism in a context that demands moral clarity and honesty. Troops makes living, breathing individuals working for all of us under often grievously dangerous conditions sound like some kind of substance, like Jell-O, or some kind of freight. There is an air of the drone strike in using troops in this way; it allows us to avoid dirtying our hands with the grisly realities of military combat.
Readers often think of Mr. Orwell amid arguments such as this one, and which we must recall that he noted, of a euphemism of this sort, that “it falls upon the facts like soft snow, blurring the outline and covering up the details.” Parents do not kiss their troop goodbye. The person learning to use a prosthetic leg is not a troop, nor was she one while serving in the conflict that saddled her with such a tragic burden. The contents of a body bag are not a troop.
My proposal is that we use the words soldier, sailor, or Marine when describing members of the armed forces. A soldier is a person; a troop is something from the game of Risk.