Soldiers of People's Liberation Army (PLA) Lanzhou Military Region jump through a burning obstacle during a training session at a military base in Tianshui, Gansu province, China, January 6, 2016. (Photo by Reuters/Stringer)

A tribal fighter loyal to Yemen's government stands in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)

Newly-wed Syrian couple Nada Merhi, 18, and Hassan Youssef, 27, have their wedding pictures taken in front of a heavily damaged building in the war ravaged city of Homs on February 5, 2016. A Syrian photographer thought of using the destruction of Homs to take pictures of newly wed couples to show that life is stronger than death. (Photo by Joseph Eid/AFP Photo)

Women pose for a picture at Havana city, Cuba, March 17, 2016. Obama arrives in Havana on Sunday for a historic visit that seals a rapprochement he and Cuban President Raul Castro agreed in December 2014 after 18 months of secret negotiations. (Photo by Ivan Alvarado/Reuters)

A model poses backstage ahead of the NLP show at Mercedes-Benz Fashion Week Australia 2014 at Carriageworks on April 7, 2014 in Sydney, Australia. (Photo by Brendon Thorne/Getty Images)

A 41-year-old man going by the name of Chibatman rides his “Chibatpod” on the road in Chiba, east of Tokyo, August 31, 2014. The man, who dresses up as the comic book superhero Batman, came up with his moniker after adding a prefix of the first three letters of the city name, of which he roams on his three-wheeled motorcycle. However, unlike the hero from the Batman series, he rides around in his machine, designed from inspiration of the “Batpod” from the movies The Dark Knight and The Dark Knight Rises, delivering smiles instead of fighting crime. (Photo by Yuya Shino/Reuters)

Members of the U.S. Army 173rd Airborne Brigade stand at attention as a Ukrainian folk dance group performs at the opening ceremony of the “Rapid Trident” NATO military exercises on September 15, 2014 near Yavorov, Ukraine. The two-week exercises include participating units from a variety of NATO and NATO-associate countries as well as Ukrainian troops. Meanwhile fighting between pro-Russian separatists and Ukrainian armed foces has flared again in eastern Ukraine in a battle for the control of Donetsk airport despite the tenuous ceasefire. (Photo by Sean Gallup/Getty Images)

A Houthi follower with fake blood on his clothes lies on the ground to represent a victim as others perform a war dance during a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)