World Leaders Gather For Nuclear Security Summit 2014

THE HAGUE, NETHERLANDS - MARCH 25: British Prime Minister David Cameron (L) and U.N. Secretary General Ban Ki-moon speak with one another during bilateral talks at the 2014 Nuclear Security Summit on March 25, 2014 in The Hague, Netherlands. Leaders from around the world have come to discuss matters related to international nuclear security, though the summit is overshadowed by recent events in Ukraine. (Photo by Sean Gallup/Getty Images)