Street fighting in Berlin between Government troops and Spartacists, during the Spartacist uprising which followed Germany's defeat in World War I. (Photo by Keystone/Getty Images). 1919

“Weapons Instructor”, 2012. It’s a well known fact that the IDF trains some of the best soldiers in the world, but at the source of every good soldier lies an exceptional instructor – and that’s where Cpl. Daniella Stepanoe steps in. She travels from base to base training everyone from paratroopers to elite special forces units in the use of their weapons. (Photo by Israel Defense Forces)

A monkey is led by its trainer Qi Defang during training for a circus in Suzhou, Anhui province, November 29, 2014. Suzhou is known as the hometown of circus troupes in China and has more than 300 circus troupes. (Photo by William Hong/Reuters)

A Tengger tribesman prays at Mount Bromo during the annual Kasada ceremony in East Java on August 12, 2014. The Kasada ceremony is a festival held every 14th day of the Kasada month in the traditional Hindu lunar calender to honour Sang Hyang Widhi (God Almighty) and is based on the legend of Roro Anteng and Joko Seger from the Majapahit Kingdom, from which their Tengger tribe name originates. Hundreds of worshippers from the Tengger tribe offer food and livestock as a symbolic sacrifice which they throw into the crater for the blessings of safety and prosperity to their familyies and community. (Photo by Juni Kriswanto/AFP Photo)

A citizen rides in smog on December 20, 2016 in Jinan, Shandong Province of China. Air quality index (AQI) readings exceeded 400 and some schools have suspended classes in Jinan. (Photo by VCG/VCG via Getty Images)

An armed youth loyal to the Houthi movement takes part in a protest against the Saudi-backed exiled government deciding to cut off the Yemeni central bank from the outside world, in the capital Sanaa, Yemen August 25, 2016. (Photo by Mohamed al-Sayaghi/Reuters)

US marines watch the mushroom cloud from an atomic explosion rise above the Yucca flats, Nevada during a US nuclear weapons test. (Photo by Keystone/Getty Images). USA, 1945

A fruit importer's lorry at Covent Garden, London, with its driver's cabin in the shape of an apple. (Photo by Harold Clements/London Express/Getty Images). October 1928