Sixty years after the horrors of Hiroshima and Nagasaki, the Japanese are beginning -- with a gentle nudge from Washington -- to talk openly about the long-forbidden subject of nuclear weapons.The post-World War II pacifism under which Japan's military is known as a "self-defense force" remains strong. But the rise of China and North Korea's nuclear ambitions have spurred what is referred to here as "active pacifism," or a more pragmatic line on defense.