Gas-masked men of the British Machine Gun Corps with a Vickers machine gun during the first battle of the Somme, 1916. (Photo by General Photographic Agency/Getty Images)

NEPAL: A devotee is smeared with a vermillion powder while celebrating the “Sindoor Jatra” vermillion powder festival at Thimi, in Bhaktapur, Nepal, April 14, 2016. (Photo by Navesh Chitrakar/Reuters)

A woman stands at the door of her shanty at a slum in Mumbai, India July 20, 2016. (Photo by Danish Ismail/Reuters)

In this July 24, 2016 photo, a pilgrim takes a bath in a sacred mud pool during the annual Voodoo celebration in Plaine-du-Nord, Haiti, Saturday, July 23, 2016. Pilgrims come to bathe in the mud and make offerings expecting a miracle. (Photo by Dieu Nalio Chery/AP Photo)

A woman waits at a polio immunisation health centre, in Maiduguri, Borno State, Nigeria, August 29, 2016. Nigeria's military has liberated large swathes of land from Boko Haram but a ride with an army convoy, all guns firing for fear of ambush, shows how far the northeast is from normality after a brutal Islamist insurgency that has displaced millions. (Photo by Afolabi Sotunde/Reuters)

In this Feb. 17, 2017 photo, surfers walk to La Pampilla beach in Lima, Peru. Night surfing apparently came about in Lima because of a dispute with the capital municipality that in 2015 increased the width of a road that runs along the coast. The surfers protested the construction for months by camping on the asphalted beach area, but in the end the municipality prevailed, with support from the police. At the end of 2016, perhaps to win over the surfers, Lima's mayor set up beach lights that allows for night surfing. (Photo by Rodrigo Abd/AP Photo)

A boy dressed as Hindu Lord Shiva poses before performing in a religious procession at the Mahashivratri festival in Allahabad, India, March 7, 2016. Hindus across the country celebrate Mahashivratri, better known as Lord Shiva's wedding anniversary. (Photo by Jitendra Prakash/Reuters)

This file photo provided on Sunday February 15, 2015 by the Syrian anti-government activist group Aleppo Media Center (AMC), which has been authenticated based on its contents and other AP reporting, shows Syrian rebels firing locally made shells against the Syrian government forces, in Aleppo, Syria. (Photo by AP Photo/Aleppo Media Center)