Barack Obama will be the first U.S. president to visit Japan's city of Hiroshima. It is a big event for the USA and Japan. Hiroshima is the first city to suffer from atomic weapons. Around 140,000 people died in 1945 after the bomb fell on the city. Historians say it helped end World War II. Others say it should never have happened. Mr Obama will not apologise for the bombing. He will look to a future that focuses on the USA and Japan working together.
Barack Obama has wanted to visit Hiroshima for many years. Mr Obama said his visit would be a time to think about how bad war is, and to remember the dead. He wants to remind people that war causes unnecessary death and that nuclear weapons should never be used. He said innocent people caught in war suffer a lot. He added: "And that's not just the thing of the past. That is happening today in many parts of the world."