John J. Mearsheimer

After the Cold War, Francis Fukuyama, Samuel Huntington, and John Mearsheimer each presented a bold vision of what the driving forces of world politics would be. The world in 2010 hardly seems on a more promising track -- a reminder that simple visions, however powerful, do not hold up as reliable predictors of particular developments.

The traditional goal of America's foreign policy has been to prevent the rise of a peer competitor. Washington sends troops abroad only when a potential hegemon arises that others cannot contain. Europe and Northeast Asia are quiet now, so the United States will likely withdraw its forces over the next decade or so, throwing those regions back into familiar great-power rivalry. Over time, however, China could become the most powerful rival the United States has ever faced-and Washington's policies since the end of the Cold War have been speeding Beijing's rise rather than slowing it.

Conventional wisdom argues that Ukraine should be forced to give up its nuclear weapons to ensure peace and stability in Europe. This is quite wrong. As soon as Ukraine declared its independence, Washington should have encouraged Kiev to fashion its own secure nuclear deterrent. The dangers of Russian-Ukrainian rivalry bode poorly for peace. If Ukraine is forced to maintain a large conventional army to deter potential Russian expansion, the danger of war is much greater than if it maintains a nuclear capability. U.S. policy should recognize that Ukraine, come what may, will keep its nuclear weapons.