Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

A refugee sits in front of a Greek riot police cordon during a protest at the Greek-Macedonian border, near the Greek village of Idomeni, March 1, 2016. (Photo by Alexandros Avramidis/Reuters)

A girl covers her face as she is daubed in colours during the religious festival of Holi inside a temple in Nandgaon village, in the state of Uttar Pradesh, India, March 5, 2020. (Photo by Adnan Abidi/Reuters)

An orphan plays with her new hula hoop during the food and toy distribution, for total about 500 orphans in 11 orphanages, by National Muslim COVID-19 Response Committee to celebrate Eid al-Fitr, the Muslim holiday which marks the end of the fasting month of Ramadan at Good hope markazil Banatil Islamia orphans centre in Nairobi, Kenya, on May 25, 2020. (Photo by Yasuyoshi Chiba/AFP Photo)

German troops in Stalingrad, USSR. September 10, 1942. (Photo by TASS)

Senior Buddhist monk Lobsang Tayang sits outside the Amarbayasgalant Monastery in the Baruunburen district, Selenge province, Mongolia, April 26, 2018. (Photo by Thomas Peter/Reuters)

Alexandra Mazo, 12, with her cellphone on her way down the mountain after finishing school. The remote mountain village of Pueblo Nuevo has been highly affected by the armed conflict and direct combat between the national army and Farc guerrillas due to its strategic location and the intensive production on coca crops on the surrounding hillsides. (Photo by Mads Nissen/Politiken/The Guardian/Panos Pictures/The Nobel Peace Center)

A boy dressed as Lord Krishna is pictured while Hindu devotees march on the streets to celebrate Janmashtami festival, which marks the birth anniversary of Lord Krishna, in Dhaka, August 14, 2017. (Photo by Mohammad Ponir Hossain/Reuters)