Romanian soldiers take part in a joint military exercise with NATO members, called “Agile Spirit 2015” at the Vaziani military base outside Tbilisi, Georgia, July 21, 2015. Georgian soldiers along with U.S. marines and platoon-size units from Bulgaria, Latvia, Lithuania and Romania are taking part in the exercises at the Vaziani military base outside Tbilisi. (Photo by David Mdzinarishvili/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)

Yussef Saluta (R), 20, an Israeli Arab soldier from the Desert Reconnaissance battalion takes part in a drill near Kissufim in southern Israel November 29, 2016. A battalion of soldiers crawls across the desert sand with assault rifles cocked. It's a routine exercise, but these are no ordinary troops – they are Arabs who have chosen to fight for the Jewish state. (Photo by Amir Cohen/Reuters) (Photo by Amir Cohen/Reuters)

A suspected Vietcong is kicked by a Vietnamese soldier holding a rifle as another soldier attempts to tie his hands on October 22, 1965. The prisoner was one of 15 captured October 21 near Xom Chua when government troops raided in the plain of reeds area. Troops killed 43 suspected Vietcong and seized some arms. (Photo by Richard Merron/AP Photo)

Russian soldiers rehearse ahead of a forthcoming parade on Red Square in Moscow on November 5, 2017 The event will take place on November 7, marking the 76 th anniversary of a 1941 parade, when Red Army soldiers marched past the Kremlin walls towards the front line to fight Nazi Germany troops during World War Two. (Photo by Mladen Antonov/AFP Photo)

Soldiers are reflected in a puddle during a military parade during the celebrations for Romania's National Day in Bucharest December 1, 2014. (Photo by Radu Sigheti/Reuters)

People dressed as Hungarian Hussars fire a cannon during re-enactment of the battle against Austrian soldiers of the Habsburg dynasty in Tapiobicske, Hungary April 4, 2016. (Photo by Laszlo Balogh/Reuters)

An army dog stands up as retiring soldiers salute their guard post before retirement in Suqian, Jiangsu province, China on November 29, 2017. (Photo by Reuters/China Stringer Network)