Members of the Bavarian police and the Bundeswehr, the German armed forces, guard a vehicle checkpoint as they demonstrate a dynamic operation as part of the GETEX anti-terror exercises during a media event on March 9, 2017 in Murnau, Germany. (Photo by Philipp Guelland/Getty Images)

Warriors from the Suri tribe in Ethiopia still stage the savage “Donga” battles – even after many fighters have been died from their injuries. Donga stick fights take place after the harvests, the Surmas count days owing to knots on a long stem of grass or jags on the trunk of a tree dedicated to that specific use. Here: A tribeswoman sporting a huge lip plate and wearing a skinned animal carcass on her head. (Photo by Eric Lafforgue/Exclusivepix Media)

For centuries the Highlands peoples of Papua New Guinea fought over land, women and pigs. Sorcery and battle skills could elevate a clan to Bigmanship, where the bigger the “presentation”, the bigger the man. Clans therefore would paint their bodies and create fearsome masks as part of their psy. Here: These are the terrifying tribe of “mudmen” from a remote part of Papua New Guinea. (Photo by Jeremy Hunter/Exclusivepix Media)

People in hard hats in a rage room in Moscow, Russia on January 27, 2016. The Debosh stress relief service gives its customers an opportunity to smash the rage room up with sledgehammers and bats to relieve stress and tension. (Photo by Artyom Geodakyan/TASS/Barcroft Media)

Emergency services work at the scene of a bus accident on the Kingsway in central London February 2, 2015. A number 91 double-decker bus had its roof ripped off after hitting a tree, causing injury to passengers and passers-by, local media reported. (Photo by Peter Nicholls/Reuters)

Participants demonstrate for the media before the role play event at Czocha Castle in Sucha, west southern Poland April 9, 2015. Harry Potter enthusiasts from all over the world are attending a four-day live action role play event at the medieval castle made into a close imitation of the “College of Wizardry”. (Photo by Kacper Pempel/Reuters)

A view of one of the dioramas contained inside iron boxes as part of the “S.A.C.R.E.D” installation by Chinese artist Ai Weiwei during a media preview at the cathedral in Cuenca, Spain, July 21, 2016. Ai Weiwei has reproduced scenes of his incarceration for a new art installation, a series of almost life-size dioramas – encased in steel boxes – showing his life in jail. (Photo by Susana Vera/Reuters)

Engine driver Josef Kowatsch (top L) steers a train through the NEAT Gotthard Base Tunnel during a media visit near the town of Erstfeld August 24, 2015. Crossing the Alps, the world's longest train tunnel should become operational at the end of 2016, consisting of two parallel single track tunnels, each of a length of 57 km (35 miles). (Photo by Arnd Wiegmann/Reuters)