When President Obama won the Nobel Peace Prize in 2009, one of the primary reasons cited was his commitment to reducing the threat of nuclear weapons. On Friday, Obama once again spoke to that cause during a visit to the first site at which a nuclear weapon was used in war. A somber Obama spoke after laying a wreath on the museum's cenotaph alongside Japanese Prime Minister Shinzo Abe. During the speech, the park was silent except for a circling helicopter, chirping birds and camera shutters. Obama said there is a "shared responsibility" to look into the "eye of history" and ask what must be done to prevent another nuclear weapon being used. One thing that Obama did not do: apologize.