United Nations Secretary General Ban Ki-moon arrived in Japan Tuesday to visit Hiroshima and Nagasaki, the two cities where the US military dropped atomic bombs 65 years ago, reported dpa. Ban will be the first UN secretary general to attend the Peace Memorial Ceremony in Hiroshima. The former South Korean foreign minister is to visit memorials to Korean victims of the atomic bombing as well as Japanese victims in both cities. The UN chief told Kyodo News in New York before his departure for Japan Monday of his commitment to realize a world without nuclear weapons within his lifetime.