A competitor scrambles in the mud under barbed wire during the Tough Guy Challenge 2009 at South Perton Farm on February 1, 2009 in Wolverhampton, England. The biannual event to raise cash for charity challenges thousands of international competitors to run through a gruelling set of 21 obstacles including water, fire and tunnels after a lengthy run at the start. (Photo by Christopher Furlong/Getty Images)

A military instructor teaches a schoolboy shooting with Kalashnikov rifles, during a training session at a military unit of the National Guard of Ukraine in western Ukrainian city of Lviv on February 15, 2022. (Photo by Yuriy Dyachyshyn/AFP Photo)

Participants from a North Korea military band perform during the Spasskaya Tower international military music festival in Red Square in Moscow, Russia, Friday, August 23, 2019. (Photo by Alexander Zemlianichenko/AP Photo)

A woman takes a selfie in front a damaged Turkish military APC that was attacked by protesters near the Turkish military headquarters in Ankara, Turkey, Saturday, July 16, 2016. (Photo by Hussein Malla/AP Photo)

Hong Kong art gallery director Sarah Greene said that Wolf, known for his work depicting mega-cities, has died Tuesday, April 24, 2019 night at his home. She said he was 64. Wolf won first prize in the World Press Photo competition in 2005 and 2010. Here: Architecture of Density #119, 2009. (Photo by Michael Wolf, courtesy of Flowers Gallery)

A military instructor helps a boy to shoot a rifle with blanks at a weapon exhibition during a military show in St.Petersburg, Russia, Sunday, January 17, 2016. (Photo by Dmitry Lovetsky/AP Photo)

Libyan leader Muammar Gaddafi attends the inauguration ceremony of Jacob Zuma on May 9, 2009 in Pretoria, South Africa. Jacob Gedleyihlekisa Zuma is South Africa's fourth President since the end of apartheid. (Photo by Foto24/Gallo Images/Getty Images)

Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)