U.S Army combat camera photographer Spc. Hilda Clayton took this photo July 2, 2013 that was released by the U.S. Army, that shows an Afghan soldier engulfed in flame as a mortar tube explodes during an Afghan National Army live-fire training exercise in Laghman Province, Afghanistan. The accident killed Clayton and four Afghan National Army soldiers. (Photo by Spc. Hilda Clayton/U.S. Army via AP Photo)

Syrian Internal Security Forces dance in celebration during their graduation ceremony, at Ain Issa desert base, in Raqqa province, northeast Syria, Thursday, July 20, 2017. Some 250 residents of Syria's Raqqa province are the latest batch to graduate from a brief U.S-training course that is preparing an internal security force to hold and secure areas as they are captured from Islamic State militants. (Photo by Hussein Malla/AP Photo)

Przemek Pawlicki performs during training in Leszno, Poland on May 12, 2016. A stunning action-packed catalogue of photographs from sporting events around the world has been released by Red Bull. The energy drink giant's photographers have been busy capturing extraordinary images of action sports and some of the world's greatest daredevils. (Photo by Lukasz Nazdraczew/Red Bull/SWNS.com)

A CRH train is seen passing through Nanjing South Railway Station, which is part of the Beijing-Shanghai High-Speed Railway Line, on March 27, 2011 in Nanjing, Jiangsu Province of China. The High-Speed railway line is 1,318 kilometres long, running between Beijing and Shanghai. The line will open on June 10, 2011. (Photo by ChinaFotoPress/Getty Images)

A humanoid dental patient robot, named Hanako Showa, about to be used during a demonstration of dental treatment at Showa University on March 25, 2010 in Tokyo, Japan. The robot was co-developed by the university and tmsuk co. Ltd, and simulates real human patients. The robot has been used for training of procedures in which the dental treatment requires a high level of precision. (Photo by Koichi Kamoshida/Getty Images)

A model showcases lingerie during a lingerie show on International Women's Day at a shopping mall on March 8, 2011 in Qingdao, Shandong Province of China. The official theme of International Women's Day 2011 is “Equal access to education, training and science and technology: Pathway to decent work for women”. (Photo by ChinaFotoPress/Getty Images). QINGDAO, CHINA – MARCH 08 2011

Revelers gather on a commuter train platform of the HVV city public transportation system to drink alcohol on September 30, 2011 in Hamburg, Germany. Thousands of people participated in the event dubbed the “HVV Abschiedstrinken” (HVV Farewell Drink) that was organized through Facebook and is meant to celebrate the last day before a ban on alcohol consumption goes into effect on the city's public transport. (Photo by Joern Pollex/Getty Images)

Tree trunks lie on the railtracks that will be used to transport nuclear waste on November 25, 2011 in Leitstade, near Metzingen, Germany. A train carrying the Castor containers of processed, spent nuclear fuel started from La Hague in France Wednesday for its journey to the Gorleben temporary nuclear waste storage facility in Germany, and thousands of protesters are expected to attempt to blockade the route. (Photo by Carsten Koall/Getty Images)