Ammunition airlift into besieged Khe Sanh, Operation Pegasus, April 1968. (Photo by Larry Burrows/AP Photo)

An Afghan hunter shoots at a duck in Laghman province, Afghanistan on May 30, 2018. (Photo by Reuters/Parwiz)

In this Sunday, June 17, 2018, file photo, an Indonesian resident walks past graffiti on a downtown street in Hong Kong. There are 370,000 foreign domestic helpers in the Chinese territory and about 49.4 percent from Indonesia. (Photo by Vincent Yu/AP Photo)

An air raid drill at Seattle College caught students William Bates, left, and Edna Mae Farrell, right, while they were eating their lunch in the school café, but they simply took shelter under the table and continued eating in Seattle, Washington, March 17, 1942. Air raid wardens said 350 students left their classrooms and assembled in shelters within one minute in first at the college. (Photo by AP Photo)

Mave Grace, 11, who had part of her arm chopped off by militiamen when they attacked the village of Tchee, stands with her sister Racahele-Ngabausi, aged two, in an Internally Displaced Camp in Bunia, Ituri province, eastern Democratic Republic of Congo, April 12, 2018. (Photo by Goran Tomasevic/Reuters)

A man cries as he carries his daughter while walking from an Islamic State-controlled part of Mosul towards Iraqi special forces soldiers during a battle in Mosul, Iraq March 4, 2017. Reuters Photographer Goran Tomasevic: “Both screaming in terror, a father and the young daughter he cradled in his arm fled through the rubble-strewn streets of Wadi Hajar, transformed in a flash into a battleground between Islamic State fighters and Iraqi special forces. They and their neighbours – some wearing rubber sandals, some barefoot – were running from an IS counter-attack in this part of Mosul, dodging gunfire as the militants closed in”. (Photo by Goran Tomasevic/Reuters)

Young women flash the victory sign in front of a bonfire as Turkish Kurds gather during Newroz celebrations for the new year in Diyarbakir, southeastern Turkey, on March 21, 2017. Newroz (also known as Nawroz or Nowruz) is an ancient Persian festival, which is also celebrated by Kurdish people, marking the first day of spring, which falls on March 21. (Photo by Ilyas Akengin/AFP Photo)

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)