http://www.usatoday.com/story/opinion/2014/03/19/nuclear-weapons-ukraine-putin-russia-column/6629775/
Washington is in a weak position to extend the U.S. nuclear deterrence umbrella over Ukraine. The Obama administration has pursued a nuclear "global zero" strategy, seeking to eliminate nuclear weapons and hoping other countries will follow.
This has led to three destabilizing mistakes: drastically reducing U.S. nuclear capabilities to the point where their deterrent value is questionable; abandoning planned missile defense sites in Poland and the Czech Republic, in favor of a program that significantly reduces the U.S. ability to defend NATO allies and partners from missile attacks; and legitimizing the recent Russian nuclear buildup and modernization under the flawed 2010 New START Treaty.
The White House is now learning that the Cold War might be long over, but the rules of deterrence have not changed.