UN Secretary-General Ban Ki-moon pays tribute to peacekeepers who died in UN peacekeeping operations worldwide during a wreath-laying ceremony on the occasion of the International Day of United Nations Peacekeepers, at the United Nations headquarters in New York, United States, May 29, 2015. UN Secretary-General Ban Ki-moon on Friday led the world body in honoring peacekeepers who died in UN peacekeeping operations worldwide, while saluting those who are serving their mandates in the world's most dangerous places. (Xinhua/Li Muzi)