Jun Sato (2nd L), founder of Japan's first parkour educational institute SENDAI X-TRAIN, demonstrates his parkour skill with other practitionners at a park in Tokyo, Japan November 2, 2016. (Photo by Kim Kyung-Hoon/Reuters)

These images, scanned from old glass negatives which had surfaced in northern France, were believed to have been taken by a local amateur photographer in 1916. They showed British and a few Australian soldiers, in formal or informal poses, during or just before the most murderous battle in the history of the British Empire – Battle of the Somme. Who are these British and British Empire soldiers? The identity of the soldiers is, and may always remain, a mystery... (Property of Bernard Gardin/Dominique Zanardi/Joel Scribe/The Independent Magazine)

A South Sudanese People Liberation Army (SPLA) soldier patrols the streets in Malakal on January 21, 2014. (Photo by Harrison Ngethi/AFP Photo)

Soldiers, including two recruits who have brought some chickens, at Victoria prepare to board the train for the battle front. (Photo by Hulton Archive/Getty Images)

Soldiers try to attach the balloon to their car, June 1944. (Photo by Jared Enos/Mediadrumworld.com)

A German rifleman beside the corpse of a French soldier in a trench at Fort Vaux, France, 1916. (Photo by Hulton Archive/Getty Images)

A South Korean soldier wear North Korea's military uniform, acting as North Korean soldier during an anti-terror and anti-chemical drill session held as part of the 2011 Ulchi Freedom Guardian (UFG) event on August 17, 2011 in Seoul, South Korea. The 11-day UGC, which features drills including the handling of chemical and biological attacks, is a regular joint exercise between US and South Korean troops to prepare for potential emergencies on the Korean Peninsula. (Photo by Chung Sung-Jun/Getty Images)

Iraqi soldiers from 9th Armoured Division give drops of water to a dehydrated child rescued earlier by soldiers at the frontline, during the ongoing fighting between Iraqi forces and Islamic State militants near the Old City in western Mosul, Iraq June 13, 2017. (Photo by Erik De Castro/Reuters)