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

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)

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

A soldier helps another with her ear protection at the Terningmoen Camp in Elverum, Norway on March 23, 2017. Soldiers demonstrate their skills and tactics during a contract drill as they train to become part of the world's first all-female special forces unit, the Jegertroppen or “hunter troops”. (Photo by Carolina Reid/NBC News)

An Iraqi special forces soldier shot dead an Islamic State suicide bomber in Mosul, Iraq March 3, 2017. (Photo by Goran Tomasevic/Reuters)

Russian soldiers write home while serving on the Eastern Front during World War I, circa 1915. (Photo by Hulton Archive/Getty Images)

Israeli soldiers get ready to launch the Skylark drone during a drill on January 16, 2012 near Bat Shlomo, Israel. (Photo by Uriel Sinai/Getty Images)