A boy holds the remains of a mortar shell which hit a residential building in the village of Staromikhailovka, outside the separatist-held city of Donetsk, Ukraine, May 24, 2016. (Photo by Alexander Ermochenko/Reuters)

A cosplayer prepares before the start of the parade during the Metropoli (Media Culture and Entertainment Festival) in Gijon, northern Spain, July 3, 2016. (Photo by Eloy Alonso/Reuters)

South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)

In this photo taken on Friday, July 14, 2017, a student at a paramilitary camp for children calls the rank to attention outside Kiev, Ukraine. As the deadly conflict in eastern Ukraine entered its third year, some parents in Ukraine are anxious to make sure their children are ready to fight it, instead of swimming and playing volleyball. (Photo by Efrem Lukatsky/AP Photo)

A reveller covered in tomato pulp takes part in the annual “Tomatina” festival in the eastern town of Bunol, on August 30, 2017. The iconic fiesta – which celebrates its 72nd anniversary and is billed at “the world's biggest food fight” – has become a major draw for foreigners, in particular from Britain, Japan and the United States. (Photo by Jaime Reina/AFP Photo)

In this undated handout photograph from the “Inside Out Project”, a poster bearing the image of a Pakistani girl whose parents, lawyers say, were killed in a drone strike, lies in a field at an undisclosed location in the northwestern Khyber-Pakhtunkhwa province. A group of artists in Pakistan are hoping to generate “empathy” among US drone operators by placing giant posters of children in the country's troubled tribal regions. (Photo by AFP Photo)

Scores of internally displaced Muslims are at the heart of the humanitarian crisis in Central African Republic, where violence between Christians and Muslims has threatened to spiral into genocide. Photo: An internally displaced woman carries her child in a camp for internally displaced people (IDPs), located at Bangui International Airport, April 10, 2014. (Photo by Goran Tomasevic/Reuters)

In this photo taken Thursday, May 7, 2015 photo, remains of Soviet soldiers killed during World War II lay in a coffin prior to a reburial ceremony at the Sinyavino Heights memorial near the village of Sinyavino, 50 km (31 miles) east of St. Petersburg, Russia. Hundreds of people came to a World War II battleground outside St. Petersburg this week to bury the remains of 964 Soviet soldiers recovered by volunteer search teams. Fifty crimson coffins containing skulls and bones were solemnly buried at the Sinyavino Heights memorial as Russian war songs played and an honor guard fired a salute. (Photo by Dmitry Lovetsky/AP Photo)