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)

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

A woman waters the plants outside her house in an alley at a slum in Mumbai October 28, 2014. (Photo by Danish Siddiqui/Reuters)

Two Herens cows lock horns during the qualification round of the annual “Battle of the Queens” cow fight finals in Aproz, in the western Alpine canton of Valais May 5, 2013. Each year when taken to the alpine pastures, the cows test their strength and fight for the herd's leadership. The competition continues until a new queen has forced all the other cows to retreat. (Photo by Valentin Flauraud/Reuters)

A boy jumps from a swing during sunset in Valras-Plage, southern France December 29, 2014. (Photo by Yves Herman/Reuters)

Fans dressed up in costume await the cast members on the red carpet at the world premiere of the film "The Avengers: Endgame" in Los Angeles, California, April 22, 2019. (Photo by Mario Anzuoni/Reuters)

A mural painted on a fence depicts US President Donald Trump as the Coronavirus in San Francisco, California on April, 01, 2020. All 40 million residents of California were Thursday ordered to stay at home indefinitely in a bid to battle the coronavirus pandemic in the nation's most populous state. (Photo by Josh Edelson/AFP Photo)

An exotic dancer wears personal protective equipment while taking a tip in a drive-through go-go dance tent offered by the Lucky Devil Lounge strip club in the wake of the coronavirus disease (COVID-19) restrictions in Portland, Oregon, U.S. April 24, 2020. (Photo by Terray Sylvester/Reuters)