Student protestors, including one girl with a camera, struggle with soldiers from the Chinese Army, the PLA. Tiananmen Square, 1989. (Photo by Jeff Widener/Associated Press)

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

A fighter jet flies above as Ukrainian soldiers sit on an armoured personnel carrier in Kramatorsk, in eastern Ukraine April 16, 2014. Ukrainian government forces and separatist pro-Russian militia staged rival shows of force in eastern Ukraine on Wednesday amid escalating rhetoric on the eve of crucial four-power talks in Geneva on the former Soviet country's future. (Photo by Marko Djurica/Reuters)

A man holds up for a picture a one hundred trillion Zimbabwean dollars note inside a shop in Harare, Zimbawe, June 12, 2015. Hyperinflation in Zimbabwe was a period of currency instability that began in the late 1990s shortly after the confiscation of private farms from landowners, towards the end of Zimbabwean involvement in the Second Congo War. During the height of inflation from 2008 to 2009, it was difficult to measure Zimbabwe's hyperinflation because the government of Zimbabwe stopped filing official inflation statistics. However, Zimbabwe's peak month of inflation is estimated at 79.6 billion percent in mid-November 2008. (Photo by Philimon Bulawayo/Reuters)

Pigeons fly out from the mouth of a giant Buddha statue at Wat Nam Daeng Buddhist temple in Chachoengsao province, east of the Thai capital Bangkok, on October 11, 2020. (Photo by Mladen Antonov/AFP Photo)

An American flag flutters on a young tree stripped of bark after a massive tornado passed through the town killing at least 116 people May 24, 2011 in Joplin, Missouri. The tornado that ripped through the town of about 50,000 people May 22, is being called the deadliest single tornado in the U.S. in 60 years. (Photo by Julie Denesha/Getty Images)

A Ukrainian serviceman is seen at his position on the front line in Krasnogorivka near Donetsk, Ukraine, August 12, 2016. (Photo by Gleb Garanich/Reuters)

A girl reacts during a rehearsal for the Independence Day military parade in central Kiev, Ukraine, August 19, 2016. (Photo by Valentyn Ogirenko/Reuters)