A boy looks back while he and another boy play on a Syrian military tank, destroyed during fighting with the Rebels, in the Syrian town of Azaz, on the outskirts of Aleppo, Sunday, September 2, 2012. (Photo by Muhammed Muheisen/AP Photo)

A girl attends Friday prayers in front of an army tank in Tahrir Square in Cairo February 18, 2011. Five years ago thousands of protesters took to the streets demanding the end of the 30-year reign of President Mubarak as Egypt became the second country to join the Arab Spring. After weeks of clashes, strikes and protests across Egypt, Mubarak resigned on February 11, 2011. (Photo by Suhaib Salem/Reuters)

People watch a competitor riding a homemade vehicle without an engine on a 300-metre-track during the Red Bull Soapbox Race in Amman, Jordan September 4, 2015. (Photo by Muhammad Hamed/Reuters)

Competitors ride a home-made vehicle without an engine on a downhill track in the Red Bull Soapbox Race in Santiago, Chile, November 27, 2016. (Photo by Jonathan Faus/Reuters)

A Maori soldier runs as New Zealand's soldiers march down the Champs Elysees in Paris during a rehearsal of the annual Bastille Day military parade on July 12, 2016. (Photo by Thomas Samson/AFP Photo)

Pupils participate in a calligraphy contest to celebrate the New Year in Tokyo January 5, 2016. Over 3,000 calligraphers who qualified in competitions throughout Japan wrote resolutions or wishes onto paper sheets during the annual contest that marks the start of the new year, according to organizers. (Photo by Thomas Peter/Reuters)

A female goalkeeper saves the ball at the Mathare Environmental Conservation Youth Center during a soccer match to celebrate the International Women's day in Nairobi, Kenya, March 8, 2017. (Photo by Thomas Mukoya/Reuters)

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)