Rebels of the Revolutionary Armed Forces of Colombia (FARC) visit as they wait to have lunch in El Diamante, Colombia, Friday, September 16, 2016. FARC rebels are gathering for a congress were delegates will debate and vote on the accord reached last month with the Colombian government to end five decades of war. (Photo by Ricardo Mazalan/AP Photo)

A soldier from the African Union (AU) peacekeeping force stands guard at the site where a cargo plane carrying supplies for AU troops crash-landed outside Somalia's capital, on October 13, 2015 at Abirska, some 18 kilometres outside Somalian capital, Mogadishu. The officials said the Egyptian-owned transport plane went down after making several unsuccessful passes over the seafront airport. Two of the six crew members suffered light injuries in the crash, the officials said, but added that the plane and those on board were safe having landed in an area controlled by the Somali government and the African Union's AMISOM force. (Photo by Mohamed Abdiwahab/AFP Photo)

Planned improvements to Rio’s favelas have meant increases in rent, forcing the poorest families into squatting in unoccupied buildings. Photographer Tariq Zaidi visits the Mangueira community favela, less than 1km from the showpiece Maracanã stadium, to see what life is like for the women living there. Here: Victoria, 12, at her home in Mangueira. (Photo by Tariq Zaidi/The Guardian)

National Geographic has created “Air, Land & Sea: the 50 greatest wildlife photographs” exhibition. Here: CT4 Crocodile cave on the Salamat river. Set up with Nathan Williamson last chip rain came while we were with the nomads. (Photo by Michael Nichols/National Geographic)

U.S. Marine soldiers from 31st Marine Expeditionary Unit, Battalion landing team deployed from Okinawa, Japan, participate in the U.S. and South Korean Marines joint landing operation at Pohang seashore on March 29, 2012 in Pohang, South Korea. Though South Korean has remained technically at war with North Korea since the end of the Korean War in 1953, the tension of Korean Peninsula has again raised as Pyongyang's new leader Kim Jong-Eun administration announced to launch a “Satellite” between April 12 to 16. (Photo by Chung Sung-Jun/Getty Images)

World War II enthusiasts take part in a re-enactament to mark the 70th anniversary of the Allied landings on Anzio beach, 52 km south of Rome, on January 25, 2014. (Photo by Andreas Solaro/AFP Photo)

The land-robot “teleMAX” of German company telerob stands next to soldiers during a trial at the German army base on May 18, 2010 in Hammelburg, Germany. ELROB provides an overview of the current state of affairs in European unmanned system technology and to evaluate commercial off-the-shelf products for military use. It is to show what is feasible in robotics, to support technological developments in Europe, and to find solutions for the current military challenges. (Photo by Ralph Orlowski/Getty Images)

Yussef Saluta (R), 20, an Israeli Arab soldier from the Desert Reconnaissance battalion takes part in a drill near Kissufim in southern Israel November 29, 2016. A battalion of soldiers crawls across the desert sand with assault rifles cocked. It's a routine exercise, but these are no ordinary troops – they are Arabs who have chosen to fight for the Jewish state. (Photo by Amir Cohen/Reuters) (Photo by Amir Cohen/Reuters)