A child uses an umbrella to avoid rain falling on a fire at the northern Greek border point of Idomeni, Greece, Monday, April 25, 2016. Many thousands of migrants remain at the Greek border with Macedonia, hoping that the border crossing will reopen, allowing them to move north into central Europe. (Photo by Gregorio Borgia/AP Photo)

Alejandro Ccasa prays after waiting three days next to an empty oxygen tank for his uncle who has COVID-19 outside a refill shop where he is the first in line before it opens in Callao, Peru, early Tuesday, February 2, 2021. Ccasa said his family has one large tank and it gives about four hours of oxygen therapy. (Photo by Martin Mejia/AP Photo)

Dancers at the Windmill Theatre in London, England practice a routine wearing gas masks and hard-hats with their costumes, 1940. (Photo by Hulton Archive/Getty Images)

Peasants in the re-taken Somme District work in the fields, circa 1916- 1917, in this Library of Congress handout photo. For women 100 years ago, opportunities to work beyond the home and take part in political life were very limited. As the 20th century progressed, hard-won progress included gradually improved voting rights, while the upheaval of war pushed doors ajar as women worked as part of the war effort. U.S. Library of Congress archive photos show women's workplaces ranging from a flour mill in England to a coal mine in Belgium or Lincoln Motor Co.'s welding department in Detroit. International Women's Day is celebrated on March 8. (Photo by Reuters/Bain Collection/Library of Congress)

Plaster cast moulds of victims of the Mount Vesuvius eruption lie on a display table in a laboratory at Pompeii October 13, 2015. An expert team made up of archaeologists, radiologists, orthodontists and anthropologists began on September 2015 to use CAT scan technology (computerised axial tomography) to peer inside the plaster cast moulds of Pompeii's victims, in a study that has added more detail to previous findings. A 16-layer scan had to be used in order to penetrate the hardened plaster but the results showed up impressive skeletal remains and near perfect teeth. (Photo by Alessandro Bianchi/Reuters)

A soldier beaten by the mob (C) is protected by plain chothes policemen after troops involved in the coup surrendered on the Bosphorus Bridge in Istanbul, Turkey July 16, 2016. (Photo by Murad Sezer/Reuters)

Cars are parked near Place de la Concorde on March 12, 2014 in Paris, France. Inset: World War I, German airplanes at Place de la Concorde in Paris, wrecked by celebrating crowds on the day of the restoration of Alsace-Lorraine, November 18, 1918. (Photo by Peter Macdiarmid/Getty Images)

A recruitment drive during the First World War at Trafalgar Square, London. (Photo by Central Press/Getty Images)