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Open Image ModalMembers of Free Syrian Army clash against Syrian regime forces in Aleppo, Syria on Dec. 8, 2014. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA Syrian girl who took shelter in Turkey sleeps on the ground before she crosses into Kobani through Mursitpinar border crossing in the Suruc district of Sanliurfa, Turkey on March 6, 2015. (credit: Halil Fidan/Anadolu Agency/Getty Images)
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Open Image ModalA man prepares to attack Syrian regime forces in Aleppo, Syria, on Oct. 8, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA member of the Syrian opposition prepares to attack Syrian regime forces in Aleppo, Syria, on Oct. 8, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalSmoke rises from the Dareyya district after a Syrian Air Force barrel bomb attack in Damascus, Syria, on March 6, 2015. (credit:Majd el-Ahmad/Anadolu Agency/Getty Images)
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Open Image ModalSyrian oppositions attack Syrian regime forces in Aleppo, Syria, on Oct. 8, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalDamaged buildings are seen following clashes between regime forces and the Damascus Front in Damascus, Syria on March 6, 2015. (credit:Salih Mahmud Leyla/Anadolu Agency/Getty Images)
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Open Image ModalA Syrian man prays over the grave of his son, who was killed during shelling, at a cemetery in the rebel-held Damascus suburb of Douma, on March 5, 2015. (credit:ABD DOUMANY/AFP/Getty Images)
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Open Image ModalA member of Syrian opposition group linked to Damascus Front launches a rocket toward Assad's forces in Aleppo, Syria, on March 7, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA rocket is fired toward Assad's forces in Aleppo, Syria, on March 7, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA Syrian boy who took shelter in Turkey with his family crosses into Kobani through Mursitpinar border crossing in the Suruc district of Sanliurfa, Turkey on March 6, 2015. (credit:Halil Fidan/Anadolu Agency/Getty Images)
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Open Image ModalSyrian fire fighters put out a blaze at the scene of a reported barrel bomb strike by Syrian government forces on the Qadi Askar rebel-held district of the northern Syrian city of Aleppo, March 5, 2015. (credit:ZEIN AL-RIFAI/AFP/Getty Images)
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Open Image ModalSyrians inspect the debris of houses in Dareyya district after a Syrian Air Force barrel bomb attack in Damascus, Syria, on March 3, 2015. (credit:Stringer/Anadolu Agency/Getty Images)
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Open Image ModalA rebel fighter holds his rifle inside a damaged building during clashes between regime forces and the Damascus Front in Damascus, Syria on March 6, 2015. (credit:Salih Mahmud Leyla/Anadolu Agency/Getty Images)
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Open Image ModalSyrian opponents stage a missile attack against the Hemeimeem military airport, which was being used by the Russian military at the time, in Latakia, Syria, on Sept. 28, 2015. (credit:Ali Hafawi/Anadolu Agency/Getty Images)
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Open Image ModalSyrians search for survivors in the rubble of destroyed buildings following barrel bomb attacks by the Syrian air forces in Aleppo, Syria, on Oct. 8, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA man sits by a damaged building after Syrian regime army helicopters dropped barrel bombs in opposition-controlled territory in Aleppo, Syria, on July 16, 2014. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA man carries a child following barrel bomb attacks by Syrian air forces in Aleppo, Syria, on Dec. 23, 2013. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA member of Syria's opposition group launches a rocket toward Assad's forces in Aleppo, Syria, on March 7, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)
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Open Image ModalA member of Syria's opposition group fires toward Assad's forces in Aleppo, Syria, on March 2, 2015. (credit:Saleh Mahmoud Laila/Anadolu Agency/Getty Images)