U.S. President Barack Obama (L) and Japan's Prime Minister Shinzo Abe arrive at Hiroshima Peace Memorial Park in Hiroshima, Japan, on May 27, 2016. Obama is the first sitting U.S. president to visit Hiroshima to pay respects to the 140,000 people killed by the world's first nuclear atomic bomb in 1945 that brought World War II to a close. Photo by Keizo Mori/UPI