An empty cell block is pictured within Joint Task Force Guantanamo's Camp VI at the U.S. Naval Base in Guantanamo Bay, Cuba March 22, 2016. (Photo by Lucas Jackson/Reuters)

A man carries an injured girl after what activists said were five air strikes by forces loyal to Syria's President Bashar al-Assad in Douma, eastern al-Ghouta, near Damascus September 11, 2014. (Photo by Bassam Khabieh/Reuters)

A picture made available 26 April 2016 shows a tiger playing in the water with a trainer nicknamed “Super Tiger Man” at the Tiger Temple in Kanchanaburi province, Thailand, 24 April 2016. The site known in Thai as “Wat Pa Luangta Maha Bua Yannasampanno” has been the focus of a dispute with the Department of National Parks, Wildlife and Plant Conservation (DNP) after the DNP asked in 2015 that the temple hands over its 147 tigers since it was not licensed to keep them. The temple has requested for a zoo license according to its managing director. (Photo by Diego Azubel/EPA)

A Muslim boy takes part in Friday prayers on a street outside a mosque in Mumbai, India, June 24, 2016. (Photo by Shailesh Andrade/Reuters)

An Iraqi special forces soldier wears a rose in his body armor as troops move from the Yarmouk neighborhood to take another district from Islamic State militant control in Mosul, Iraq, Wednesday, April 12, 2017. (Photo by Maya Alleruzzo/AP Photo)

Ammunition airlift into besieged Khe Sanh, Operation Pegasus, April 1968. (Photo by Larry Burrows/AP Photo)

Filipino children play as they are doing caroling activities on the street near an airport, days before Christmas in Manila, Philippines, 20 December 2017. Filipinos celebrate the longest Christmas in the world which starts as early as September every year. (Photo by Francis R. Malasig/EPA/EFE)

A jogger runs on the bank of Donaukanal channel in central Vienna, Austria, September 5, 2016. (Photo by Heinz-Peter Bader/Reuters)