Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

Staff of a boat restaurant on the Taedong River line up at the entrance as they wait to greet customers Sunday, June 18, 2017, in Pyongyang, North Korea. The boat is berthed along the river, which is the fifth longest river on the Korean Peninsula and runs through the country's capital, Pyongyang. (Photo by Wong Maye-E/AP Photo)

Greyhounds with stuffed and sprung model monkeys strapped to their backs before a hurdle race at Wellinborough. (Photo by E. Bacon). 21st April 1928

Astronaut Edwin E. Aldrin Jr. walks near the Lunar Module during the Apollo 11 extravehicular activity July 20, 1969 on the Moon. (Photo by NASA/Newsmakers)

A horse-drawn cart passing through a section cut out of the base of a giant sequoia tree in the Mariposa groves of Yosemite Park, California. (Photo by Carleton E Watkins/Getty Images). 1870

Police fire rubber bullets as they help an Atletico Paranaense fan during clashes between Vasco da Gama soccer fans and Atletico Paranaense fans at their Brazilian championship match in Joinville in Santa Catarina, on December 8, 2013. Dozens of fans fought a savage battle on the terraces at the match on Sunday, interrupting play for more than one hour and leaving at least three people reportedly in serious condition. (Photo by Carlos Moraes/Agência O DIA)

The Boeoegg, a giant symbolic snowman made of wadding and and filled with firecrackers burns on top of a bonfire in Sechselaeuten square on April 24, 2017 in Zurich. When the bells of the Saint Peter's church chime six o'clock, the bonfire under the snowman is set in fire and the guildsmen wearing historical costumes ride around the bonfire. The faster the head of the snowman explods the warmer and more beautiful the summer will be. (Photo by Michael Buholzer/AFP Photo)

North Korean women soldiers take part in a military parade Saturday, April 15, 2017, in Pyongyang, North Korea, to celebrate the 105th birth anniversary of Kim Il Sung, the country's late founder and grandfather of current ruler Kim Jong Un. (Photo by Wong Maye-E/AP Photo)