Russian soldiers write home while serving on the Eastern Front during World War I, circa 1915. (Photo by Hulton Archive/Getty Images)

Soldiers are reflected in a puddle during a military parade during the celebrations for Romania's National Day in Bucharest December 1, 2014. (Photo by Radu Sigheti/Reuters)

Ngorongoro Crater (Tanzania). At 610m deep and 260 sq km, this is the largest unflooded caldera in the world. A blue-green vision from above it's a haven for engangered wildlife and Maasai livestock. The crater was formed three million years ago when a giant volcano, which could have been as high as Kilimanjaro, exploded and collapsed. The caldera formed the concentric fractures in the crust cracked down to a magma reservoir deep underground. (Photo by John Bryant/Getty Images)

Pakistan girls make selfies holding a Pakistan-made weapon displayed at the four-day International Defence Exhibition and Seminar (IDEAS) 2016 in Karachi, Pakistan, Wednesday, November 23, 2016. (Photo by Shakil Adil/AP Photo)

Two holidaymakers amuse themselves with a porter's trolley whilst waiting for their train at Euston Station, London, 5th August 1939. (Photo by A. J. O'Brien/Fox Photos/Getty Images)

Naked footballers participate in a Germany v Netherlands soccer match in protest against what they say is increasing commercialization of professional football, in Wuppertal, Germany on September 6, 2020. (Photo by Leon Kuegeler/Reuters)

Three pals pose for a picture on a night out in Liverpool city centre, United Kingdom on December 24, 2020. Festive boozers braved the cold in Liverpool and York – as millions down South rang in Christmas Day indoors due to Covid restrictions. (Photo by David Nelson/South West News Service)

Reality TV personality Kim Kardashian speaks alongside US President Donald Trump during a second chance hiring and criminal justice reform event in the East Room of the White House in Washington, DC, June 13, 2019. (Photo by Saul Loeb/AFP Photo)