Seventy years ago today, a United States Air Force B-29 bomber called Bockscar dropped the plutonium bomb "Fat Man" on the Japanese city of Nagasaki. Along with "Little Boy," which targeted Hiroshima three days before, the Aug. 9 bomb helped bring World War II to a close. The United States had become the first country to deploy nuclear weapons in wartime. Today it is still the only nation to have done so. Over the last seven decades, legions of scholars have picked apart the implications of atomic weapons, the nature of their deployment during the closing stages of the war and the immediate aftermath of the August 1945 bombings. Even with the end of the Cold War — the nuclear stalemate that characterized the post-war years — the scientific debates and dilemmas encountered by the United States and other countries that developed nuclear programs are still relevant.