The nature of world politics has changed more rapidly in the past four years than anyone expected. From the fall of the Berlin Wall up to the financial crisis of 2008, the United States had enjoyed a unprecedented period of hegemony. A decade ago, the US defense budget by itself was larger than the combined defense budgets of all other countries in the world combined, and the US felt free to launch a “war of choice” in Iraq. While the US remains the dominant military power, its weakened financial condition today means that it is much less willing to use it. The Obama administration’s reluctance to take leading roles in the crises in Libya, Syria, and now Mali are evidence of a shift to a much more passive role. And with the ongoing euro crisis, it is not clear than the European powers are going to fill in this void anytime soon.