You can’t do it, if you are sorounded by armed hostile population without huge army to place it on border. I don't think they will not want do it, but they will not be able do it.
Discussion
I think you're overlooking how conformist a large chunk of the population can be, and how they will justify almost anything if it is necessary for survival under the new conditions. On top of that, you have opportunists who will gladly collaborate. Yes, many of the best people will leave—but they will make up only a small fraction of the population.