A Saudi soldier fires a mortar towards Houthi movement position, at the Saudi border with Yemen April 21, 2015. (Photo by Reuters/Stringer)

American soldiers leaping from an armoured personnel carrier during exercises in Korea, 17th March 1954. (Photo by Three Lions)

Peru, Iquitos. Restaurant in Bellavista, an area by the Amazon on April 2005. (Photo by Jean-Claude Coutausse)

Wakhi nomad women milk yaks in Wakhan, Afghanistan. About 12,000 villagers live at an altitude of 4,500 metres in the harsh, desolate terrain. The Wakhi people live a simple, relaxed life with their livestock. (Photo by Eric Lafforgue/Barcroft Images)

A Buddhist nun walks along a path as a stupa is seen at a temple in Anuradhapura, Sri Lanka October 16, 2016. (Photo by Dinuka Liyanawatte/Reuters)

Supporters of the United Democratic Party (UDP) opposition alliance presidential candidate, Adama Barrow attend a campaign rally in Buffer zone, Gambia November 29, 2016. (Photo by Thierry Gouegnon/Reuters)

A Maasai moran athlete has his face smeared with red ocher paint during preparations for the 2016 Maasai Olympics at the Sidai Oleng Wildlife Sanctuary, at the base of Mt. Kilimanjaro, near the Kenya-Tanzania border in Kimana, Kajiado, Kenya December 10, 2016. (Photo by Thomas Mukoya/Reuters)

A woman walks past a stall at a market in Banjul, Gambia December 15, 2016. (Photo by Afolabi Sotunde/Reuters)