Russian soldiers from 34th motorized infantry mountain brigade, 58th Army, prepare to evacuate a fellow soldier acting as an injured person during a drill at the Darial range outside Russia's city of Vladikavkaz, July 28, 2010. (Photo by Kazbek Basayev/Reuters)

Afghan National Army (ANA) soldiers sit waiting to return their weapons after a day of traning at the Kabul Military Training Center (KMTC) October 3, 2010 in Kabul, Afghanistan. There are between 5,000 to 7,000 troops on the training facility in eight-week cycles trained by the coalition forces to ultimately take over the role of military operations in the country. (Photo by Paula Bronstein/Getty Images)

Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)

A simulated casualty is evacuated during an emergency services exercise at the disused Aldwych underground station on February 22, 2012 in London, England. Operation Forward Defensive aims to test the response to a terrorist incident on the London Underground network during the 2012 Olympic Games. (Photo by Peter Macdiarmid/Getty Images)

Bikers ride along the High Street as they take part in the Ride Of Respect to raise money for service veterans on April 3, 2011 in Wootton Bassett, England. The ride, which involved 10,000 bikers and started at Hullavington airfield, aims to honour the people of Wootton Bassett and to raise money for the Afghan Heroes charity.

Passengers ride an articulated bus known as a “bendy bus” on December 9, 2011 in London, England. The last remaining bendy bus will go out of service at midnight. London Mayor Boris Johnson called them cumbersome and pledged to remove them. 500 new buses are being introduced as replacements. (Photo by Peter Macdiarmid/Getty Images)

A policeman aims his weapon in Istanbul, Turkey July 16, 2016. Members of Turkey's armed forces said they had taken control of the country Friday as explosions, gunfire and a reported air battle between loyalist forces and coup supporters erupted in the capital. President Erdogan remained defiant and called on people to take to the streets to show support for his embattled government. (Photo by Kemal Aslan/Reuters)