Nuclear security was one of President Obama's top priorities in the Senate, and now he's taking the cause to the world stage. This morning he delivered a major speech in Prague outlining a plan for reducing nuclear stockpiles around the world as well as a variety of measures to halt future nuclear proliferation. Speaking before a crowd of 20,000 only hours after North Korea's missile launch, Obama said the U.S. would support the Comprehensive Test Ban Treaty to try to create a global ban on nuclear explosions for any purpose and would increase efforts to secure loose nuclear materials to prevent them from falling into terrorists' hands. "The existence of thousands of nuclear weapons is the most dangerous legacy of the Cold War," Obama said. "Today the Cold War has disappeared, but thousands of weapons have not."