President Barack Obama’s speech in Prague in April 2009 signaled a profound shift in US thinking about nuclear weapons and imparted renewed momentum to the nuclear disarmament movement. No supporter of this cause has any illusions about the obstacles that lie in the path of its realization. Indeed, a number of otherwise sympathetic analysts believe that the ambition is unrealizable, no matter how desirable it may be. Yet even if a world free from nuclear weapons is impossible, there is little dispute that a reduction in the number of such weapons is good in its own right.