In 1945, the US became the first nation to use a nuclear weapon when it dropped bombs on Hiroshima and Nagasaki. Since then, no other country has followed suit. But the threat of nuclear catastrophe hangs over the world as others build up their arsenals. In the early months of his first term as President Obama promised, "The United States will take concrete steps towards a world without nuclear weapons. To put an end to Cold War thinking, we will reduce the role of nuclear weapons in our national security strategy, and urge others to do the same." That speech earned him the Nobel Peace Prize. But, in the last days of his second term, he's continuing to modernize America's arsenal — and approving a so-called "smart bomb" — potentially more usable than ever. Isn't it reasonable to ask, why?"