Pope Francis has declared the use and possession of nuclear weapons to be "immoral" and demanded that possessors of those weapons give up their arsenals. His stance is a shift in the Vatican's position on this critical issue: Three decades ago, his predecessor Pope John Paul II said that such weapons were acceptable as long as they were used for deterrence and steady progress was made toward nuclear disarmament. That prospect seems more distant than ever as nuclear powers discard the few remaining nuclear arms control agreements and are ready to embark on a new round of nuclear modernization.

Francis' three-day stay in Japan was only the second visit to this country by a pontiff. John Paul II visited in 1981 and Francis retraced many of his steps. Francis began his Japan tour — his first stop was in Thailand — in Nagasaki, the cradle of Japanese Christianity, which spread from that city after St. Francis Xavier visited in 1549. He honored Christian missionaries and martyrs at the memorial of the 26 Nagasaki Martyrs who were crucified in 1597, the beginning of a campaign of anti-Christian persecution by Japanese leaders that lasted more than 250 years and drove believers underground.

While in Nagasaki, and again hours later in Hiroshima, Francis spoke out forcefully against nuclear weapons. His words were blunt: "The use of atomic energy for purposes of war is immoral," adding that "the possession of weapons is also immoral." He explained: "In a world where millions of children and families live in inhumane conditions, the money that is squandered and the fortunes made through the manufacture, upgrading, maintenance and sale of ever more destructive weapons are an affront crying out to heaven."