A man walks on the road between Nouahibou and Nouakchott, where three Spanish aid workers were abducted in Mauritania, December 3, 2009. (Photo by Rafael Marchante/Reuters)

People fly kites during the 2017 Pyostroye Nebo kite festival in Tsaritsyno Park in Moscow, Russia on August 27, 2017. (Photo by Asya Dobrovolskaya/TASS)

U.S. President Donald Trump boards Air Force One to depart for Vietnam from Beijing Airport in Beijing, China on November 10, 2017. (Photo by Jonathan Ernst/Reuters)

An Indian villager tries to tame a bull during a traditional bull-taming festival called “Jallikattu”, in the village of Palamedu, near Madurai, Tamil Nadu state, India, Monday, January 15, 2018. Jallikattu involves releasing a bull into a crowd of people who attempt to grab it and ride it. (Photo by R. Parthibhan/AP Photo)

Balloons are inflated at the Bristol International balloon fiesta in south west England August 6, 2015. Now in its 37th year, the Bristol International Balloon Fiesta is Europe's largest annual hot air balloon event in the city that is seen by many balloonists as the home of modern ballooning. (Photo by Toby Melville/Reuters)

An American soldier walks ahead of an MKIV (Mark IV) British-made tank, circa 1918. (Photo by Hulton Archive/Getty Images)

People on inflatable boats enjoy the weather on the Lake Lucerne in Sisikon, Switzerland, August 5, 2018. (Photo by Denis Balibouse/Reuters)

People are captured by FLIR (Forward-Looking Infrared) HD Thermal Imaging Cameras as they walk near the FLIR exhibit at the Las Vegas Convention Center during CES 2019 in Las Vegas on January 10, 2019. (Photo by David McNew/AFP Photo)