Pope Francis wants the nuclear arms race to end. He spoke while visiting Japan. He went to the only two cities to experience a nuclear attack – Nagasaki and Hiroshima. In Nagasaki, he condemned the "unspeakable horror" of nuclear weapons. Francis laid a wreath and prayed at a memorial. Nuclear bombs killed 140,000 people in Hiroshima and 74,000 people in Nagasaki in August 1945. The cities saw widespread devastation.

World leaders seem to want bigger nuclear arsenals. Francis believes a world without nuclear weapons is possible and necessary. He said weapons could not protect us from threats to international security. He said: "In a world where millions of children and families live in inhumane conditions, the money that is [wasted] and the fortunes made through the manufacture, upgrading, maintenance and sale of ever more destructive weapons, are an affront."