Combat troops are trained to break things and kill people. They're equipped with plenty of armored vehicles and artillery.
We may or may not be occupying Iraq, but if we've got e.g. mostly Military Police (MP) then it truly means something significant has changed.
Let's put it this way: if we were to decide to depose the current Iraqi government, would the troops we still have there be a good choice, let along our first?
I'm finding it hard to establish similar criteria for "withdrawal", however, because there are so many misleading usages of that word in the media right now. I just saw "US Withdraws From Iraq" as a headline in Google News a few minutes ago. Although the transitive usage of this verb can correctly describe a partial drawdown (as in "he withdrew part of his objection"), the intransitive usage cannot. This is a fact. It's also exactly the sort of thing Orwell was writing about.
Also,
Garbage.
I hesitated to make my original comment and double-hesitated to respond to this, but I'm giving it a try because I know you're a good commenter in general. I think a serious discussion of this topic would be interesting. It may be impossible, though, even here. If we can't discuss this civilly, let's bail.