An army tank fires during a firefight against militants linked to al Qaeda near the southern Yemeni city of Zinjibar May 30, 2012. (Photo by Reuters/Yemen's Defence Ministry)

A devotee dressed as Hindu Lord Shiva waits to participate in a parade during “Kumbh Mela” or the Pitcher Festival in Trimbakeshwar, India, August 18, 2015. The Kumbh Mela takes place four times every 12 years at four different river bank locations in India. (Photo by Danish Siddiqui/Reuters)

An Army Sikorsky VH-34s Choctaw helicopter once used to transport President Dwight D. Eisenhower sits in a field at the 309th Aerospace Maintenance and Regeneration Group boneyard Thursday, May 14, 2015 at Davis-Monthan Air Force Base in Tucson, Ariz. President Eisenhower became the first chief executive to be transported by helicopter. Presidents Eisenhower and John F. Kennedy were transported in VH-34 helicopters and VH-34's served as “Army One” from 1958 through 1963. (Photo by Matt York/AP Photo)

U.S. Corporal Stanley Suski, left, and Miss Tamako, a Geisha girl, whirl a bit of Jitterbug, in a bar, in Tokyo, Japan, on October 1, 1945. (Photo by AP Photo)

A worker fills a public bus with diesel as the bus driver and passengers look on, at a fuel station in Kolkata, India, February 1, 2017. (Photo by Rupak De Chowdhuri/Reuters)

Max Gold, 20, of NYC, cruises on his skateboard as thousands gather on the National Mall for the March for Science on Saturday, April 22, 2017, in Washington, DC. Activists and scientists descend on the nation's capital to rally for environmental causes and government policies rooted in scientific research as part of the Earth Day and March for Science rallies. (Photo by Jahi Chikwendiu/The Washington Post)

People enjoy carnival while shouting slogans of female empowerment and anti harrassment in Sao Paulo, Brazil on January 28, 2018. The carnival is marked by a lot of fun, but also has space to talk about more serious things – without losing the good mood. Parading for the first time in São Paulo, the Vaca Profana block proposed a reflection on sieges and machismo. (Photo by Cris Faga/Rex Features/Shutterstock)

A US Marine leads two Viet Cong suspects in restraints during the Tet Offensive on February 20, 1967. (Photo by Bettmann Archive/Getty Images)