Japanese Prime Minister Shinzo Abe(R) and visiting President of the United StatesBarack Obamavisit the Hiroshima Peace Memorial Park in Hiroshima, Japan on May 27, 2016. Barack Obama on Friday became the first incumbent U.S. president to visit Hiroshima since America dropped an atomic bomb on the city 71 years ago, stirring mixed feelings among the United States, Japan and the victim countries during WWII. (Xinhua/Ma Ping)