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)

American soldiers with the 173rd Airborne Brigade Battle Company, on a battalion-wide mission in the Korengal Valley, looking for caves, weapons caches and known Taliban leaders, 2007. Tanner Stichter tends to Spc. Carl Vandeberge in the bushes moments after Vandeberge was shot in the stomach during a Taliban ambush, which killed one soldier and wounded two others. (Photo by Lynsey Addario)

Bus 392 stands on the highway running from Beersheva to Eilat, with windows broken following a gun attack on August 18, 2011 near the Israel - Egypt border, Israel. A series of coordinated gun and roadside bomb attacks against miltary and civilian targets near the Israeli - Egyptian border, including an ambush on the bus travellling 20km north of Eilat, are reported to have left 5 dead and many injured. (Photo by Yehuada Ben Itah/Getty Images)

A reveler wearing sheepfur costume is seen in front of a bonfire on which they burn a coffin symbolizing winter during the closing ceremony of the traditional carnival parade in Mohacs, 189 kms south of Budapest, Hungary, 07 February 2016. The carnival parade of people, the so-called busos, dressed in such costumes and frightening wooden masks, using various noisy wooden rattlers is traditionally held on the seventh weekend before Easter to drive away winter, and is a revival of a legend, which says that ethnic Croats ambushed the Osmanli Turkish troops, who escaped in panic seeing the terrifying figures during the Turkish occupation of Hungary. (Photo by Tamas Soki/EPA)

View of a Spitfire from the cockpit of an He111,somewhere over Southern England 1941 – 2014. (Photo by Adam Surrey)

Singers “Elle & The Pocket Belles” attend day 3 “Ladies Day” of the Qatar Goodwood Festival on August 3, 2017 in Chichester, England. (Photo by David Hartley/PA Wire)

A suspected Vietcong is kicked by a Vietnamese soldier holding a rifle as another soldier attempts to tie his hands on October 22, 1965. The prisoner was one of 15 captured October 21 near Xom Chua when government troops raided in the plain of reeds area. Troops killed 43 suspected Vietcong and seized some arms. (Photo by Richard Merron/AP Photo)

A Chinese shopper sleeps on a bed in the showroom of the IKEA store on July 6, 2014 in Beijing, China. Of the world's ten biggest Ikea stores, 8 of them are in China to cater to the country's growing middle class. The stores are designed with extra room displays given the tendency for customers to make a visit an all-day affair. Store management does not discourage shoppers from sleeping on Ikea furniture, even marking them with signs inviting customers to try them out. (Photo by Kevin Frayer/Getty Images)