A partially frozen Niagara Falls is seen on the American side lit by lights during sub freezing temperatures in Niagara Falls, Ontario March 3, 2014. (Photo by Mark Blinch/Reuters)

A contestant walks the runway during 2017 Miss Great Britain competition at the Mayfair A-list venue DSTRKT on May 11, 2017 in London, England. The pageant hopefuls were battling it out to represent Miss Central London. Miss Great Britain is a female beauty pageant. It is the oldest pageant in the UK, established in 1945. Following World War Two, a number of seaside resorts around the country introduced beauty contests as attractions. (Photo by Jules Annan/Barcroft Images)

Vietnamese military personnel in traditional dress take part in a parade celebrating the 40th anniversary of the end of the Vietnam War which is also remembered as the fall of Saigon, in Ho Chi Minh City, Vietnam, Thursday, April 30, 2015. (Photo by Dita Alangkara/AP Photo)

A pro-democracy demonstrator fights with a Soviet soldier on top of a tank parked in front of the Russian Federation building on August 19, 1991, after a coup toppled Soviet President Mikhail Gorbachev. The same day, thousands in Moscow, Leningrad, and other cities answered Russian Republic President Boris Yeltsin's call to raise barricades against tanks and troops. (Dima Tanin/AFP/Getty Images)

A U.S. Marine leads training on a shooting range in France in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)

Portuguese runner Adriele Silva gestures during the Great Wall Marathon at the Huangyaguan section of the Great Wall of China, in Jixian of Tianjin, China May 19, 2018. (Photo by Jason Lee/Reuters)

British soldiers inspect a captured German place in the Horseguards' Parade, London during World War I in November 1914, with the London Eye in the background as a reminder of just how much has changed in the last 100 years. (Photo by Peter Macdiarmid/Getty Images)

A woman is tattooed during the Great British Tattoo Show in Alexandra Palace in north London, Britain May 23, 2015. (Photo by Neil Hall/Reuters)