Russia rolled into Czekoslovacia(sp) and did just that. They used their own troops for fighting and enslaved the populace. It also worked for the Romans for a good while.
Once more: how do you enslave a well-armed, independent, self-sufficient populace that isn't accustomed to slavery, especially if you represent a thundering minority in their midst?
"But whether the Constitution really be one thing, or another, this much is certain--that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist." --Lysander Spooner, 1867
