Niall Ferguson:

On one issue the Republican contenders and the president they wish to replace are in agreement: the United States should reduce its military presence in the Greater Middle East. The preferred arguments are that America cannot afford to be engaged in combat operations in far-flung countries and that such operations are futile anyway.
The question no one wants to answer is what will come after the United States departs. The “happily ever after” scenario is that one country after another will embrace Western democracy. The nightmare scenario is either civil war or Islamist revolution. But a third possible outcome is a revived Ottoman Empire...

Perhaps we should guard against the possibility by cultivating an alliance with Mongolia.