An army dog stands up as retiring soldiers salute their guard post before retirement in Suqian, Jiangsu province, China on November 29, 2017. (Photo by Reuters/China Stringer Network)

Armed female members of the militant Palestinian group Islamic Jihad carry Kalashnikov assault rifles as they take part in a rally to protest against US President Donald Trump's decision to recognise Jerusalem as the capital of Israel, in Gaza City on December 11, 2017. (Photo by Mohammed Abed/AFP Photo)

North Korean soldiers march during a military parade marking the 105th birth anniversary of the country's founding father Kim Il Sung in Pyongyang, North Korea, April 15, 2017. (Photo by Damir Sagolj/Reuters)

A young visitor interacts with a baby hippopotamus swimming in its enclosure at the Berlin Zoo on January 1, 2018. Tourists and locals flocked to the zoo in the German capital on the unseasonably warm first day of the year. (Photo by Odd Andersen/AFP Photo)

An unidentified elderly woman, who was knocked over during the melee after a shot was fired in the direction of President Ford, is comforted by a passerby in San Francisco, September 23, 1975. (Photo by AP Photo)

The Clavie, a burning barrel packed with tar soaked sticks fixed on the top of a pole, is surrounded by people at the Doorie Hill on January 11, 2018 in Burghead, Scotland. People welcome in the New Year with the fire ceremony which has ancient roots dating back to the 1750s, when the Julian calendar was reformed in Britain. It is believed to bring good luck for the coming year. (Photo by Jeff J. Mitchell/Getty Images)

Sally Rand dances on a beach in St. Petersburg, Florida, February 17, 1936. (Photo by AP Photo)

British troops covered in flames from a petrol bomb thrown during a violent protest by job seekers, who say they were promised employment in the security services, in the southern Iraq city of Basra, March 22, 2004. (Photo by Atef Hassan/Reuters)