A pro-Russian rebel guards a captured former Ukrainian Army checkpoint outside Vuhlehirsk, Donetsk region, eastern Ukraine, Thursday, February 5, 2015. The rebels have closed in around the town in a strategy they triumphantly refer to as the Debaltseve cauldron. Separatists recently burst through government lines in the rural settlement of Vuhlehirsk. (Photo by Vadim Braydov/AP Photo)

Members of the Al-Baraa bin Malek batallion, part of the Free Syria Army's Al-Fatah brigade, duck to the ground as they pull a man (R) who was shot by a sniper twice in the Bustan al-Basha district of the northern city of Aleppo on October 20, 2012. (Photo by Javier Manzano/AFP Photo)

These Arab recruits line up in a barracks square in the British Mandate of Palestine, on December 28, 1940, for their first drill under a British solider. Some 6,000 Palestinian Arabs signed up with the British Army during the course of World War II. (AP Photo)

A U.S. Army crew chief flying on board a CH-47F Chinook helicopter observes the successful test of flares during a training flight in Afghanistan, March 14, 2018. (Photo by Tech. Sgt. Gregory Brook/Reuters/U.S. Air Force)

Jaime “Ka Diego” Padilla (R), spokesperson of the Melito Glor Command of the New People's Army (NPA), and Ka Kathryn (Comrade Kathryn) (L) react during their 50th founding anniversary celebration at an undisclosed location in the mountains of Sierra Madre, Philippines, 31 March 2019. (Photo by Alecs Ongcal/EPA/EFE)

Jack London was a prolific photographer in addition to his writing. Here: Salvation Army barracks in London during Sunday morning rush – men who had been given tickets during the night queuing for free breakfast, 1902. (Photo by Jack London/Courtesy of Contrasto)

Syrians try to rescue a dead body under the debris of a collapsed building after Syrian and Russian army carried out an airstrike on opposition controlled residential area at Merce neighborhood of Aleppo, Syria on September 23, 2016. (Photo by Jawad al Rifai/Anadolu Agency/Getty Images)

Iraqi army soldiers attempt to move their truck stuck in the mud near the village of Al-Boutha al-Sharqiyah, west of Mosul, on December 2, 2016, during a broad offencive by Iraq forces to retake the main hub city from Islamic State group jihadists. (Photo by Ahmad Al-Rubaye/AFP Photo)