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

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

German Nazi leader Adolf Hitler (1889 - 1945) enjoys a quiet picnic between meetings, circa 1933. Picture 196 of a series of collectable images published in Germany during the Nazi period, entitled “Deutschland Erwacht” (Germany Awakes). (Photo by Heinrich Hoffmann/Hulton Archive/Getty Images)

A Sadhu or a Hindu holy man stands on the banks of the river Ganges before taking a holy dip during “Kumbh Mela”, or the Pitcher Festival, in Prayagraj, previously known as Allahabad, India, February 3, 2019. (Photo by Adnan Abidi/Reuters)

An Orthodox child is given an icy dip in a lake in celebration of Epiphan, near the village of Vorontsovka, some 20 km from the Kyrgyz capital of Bishkek, Kyrgyzstan, 19 January 2019. People believe that bathing in blessed waters during the holiday of Epiphany strengthens their spirit and body. (Photo by Igor Kovalenko/EPA/EFE)

A child performs opera during celebrations on the eight day of Chinese Lunar New Year of the Pig, in Taizhou, Zhejiang province, China on February 12, 2019. (Photo by Reuters/China Stringer Network)

A girl looks out of a car at a checkpoint set up by Venezuelan security forces in Taguanes, Venezuela, February 21, 2019. (Photo by Andres Martinez Casares/Reuters)

Riders of the Peloton approach a cobbled section near the Arenberg forrest at the 117th Paris-Roubaix cycle race in Wallers, France on April 12, 2019. (Photo by Christophe Petit-Tesson/EPA)