U.S. soldiers from the 3rd Cavalry Regiment take part in an artillery exercise on forward operating base Gamberi in the Laghman province of Afghanistan December 24, 2014. (Photo by Lucas Jackson/Reuters)

Palestinian militants from al-Husine brigade loyal to Fatah movement exits from a tunnel during during a military-style exercise graduation ceremony in Khan Younis in the southern Gaza Strip, September 20, 2015. (Photo by Suhaib Salem/Reuters)

In this Friday, February 27, 2015 photo, an Israeli high-school senior preparing to join the Israeli military later this year participates in a privately run training camp for military combat fitness near Yakum, central Israel. With a mandatory three-year military service looming after graduation, teenage boys, and increasingly girls too, are gearing up for the draft, getting into shape and trying to improve their chances of acceptance into elite combat units. (Photo by Oded Balilty/AP Photo)

BAZ-69092-012 special wheeled chassis. Exhibition of military vehicles at Bronnitsy test range (a town in Moscow Oblast, Russia, located 54.5 kilometers (33.9 mi) southeast of central Moscow). Juny 10, 2011. (Photo by Vitaly Kuzmin)

A girl has her helmet adjusted on the top of a tank during the Children's Day celebration at a military facility in Bangkok, Thailand January 9, 2016. Army barracks opened their doors to children to interact with their weapons and vehicles as part of the celebration. (Photo by Jorge Silva/Reuters)

A Palestinian student jumps through a fire ring during a military-style show at a school in Rafah in the southern Gaza Strip March 28, 2016. (Photo by Ibraheem Abu Mustafa/Reuters)

A female honor guard has lipstick applied as they prepare for an official welcoming ceremony outside the Great Hall of the People in Beijing, China on June 11, 2014. (Photo by Jason Lee/Reuters)

Boys dressed in historical uniforms stand before a military parade in Red Square in Moscow November 7, 2014. The parade marked the anniversary of the 1941 parade when Soviet soldiers marched through the Red Square towards the front lines of World War Two. (Photo by Maxim Shemetov/Reuters)