A line of soldiers firing handguns during a training session, circa 1920. (Photo by Keystone). P.S. All pictures are presented in high resolution.

Three Chinese soldiers at the time of a civil war in China. (Photo by General Photographic Agency/Getty Images). 1922

Two female soldiers have their picture taken by an army colleague at Mangyongdae. (Photo by Gavin John/Mediadrumworld.com)

A soldier walks on the bank of the river in central Pyongyang, North Korea on April 16, 2017. (Photo by Damir Sagolj/Reuters)

A National Army of Colombia soldier, who was wounded by a mine, swims at a pool in Bello, municipality of Antioquia, March 25, 2015. (Photo by Fredy Builes/Reuters)

An American soldier walks ahead of an MKIV (Mark IV) British-made tank, circa 1918. (Photo by Hulton Archive/Getty Images)

A soldier eats ice cream as she visits a zoo in Pyongyang, North Korea, September 12, 2018. (Photo by Danish Siddiqui/Reuters)

American soldiers leaping from an armoured personnel carrier during exercises in Korea, 17th March 1954. (Photo by Three Lions)