These black-and-white photos are taken from the new book “Armoured Warfare in the First World War 1916 – 1918” by Anthony Tucker-Jones and published by Pen & Sword Military. Here: British troops hitch a ride on a Mark IV after the massed tank fleet spearheading attack at Cambrai on November 20, 1917. (Photo by Anthony Tucker-Jones/Mediadrumworld.com)

A girl is seen in a bakery in the old walled town of Harar in eastern Ethiopia, May 19, 2015. Daily life of people in Ethiopia, where elections are held this weekend, is portrayed in the east African nation's churches and mosques, coffee shops and markets, both in the capital Addis Ababa and the walled town of Harar in the east. Ethiopia, home to nearly 100 million people, holds the first poll on Sunday since long-serving leader Meles Zenawi died in 2012. (Photo by Siegfried Modola/Reuters)

The hard-worked hands of Jacaba Coaquira, 80, holding the green beans she grew on her land. This year the production of her land was affected by lack of rain and early cold weather that froze the crops before they finished growing. Santiago de Okola, Bolivia. (Photo by Renée C. Byer/Living on a Dollar a Day)

Russia's President Vladimir Putin (L) reacts as he talks to Belarus' President Alexander Lukashenko before a meeting on resolving the Ukrainian crisis in Minsk, February 11, 2015. A document seen by Reuters at talks on the Ukraine crisis suggested the sides may agree to end fighting in eastern Ukraine with a ceasefire starting on February 14, the withdrawal of heavy weapons and the creation of a security zone. (Photo by Mykola Lazarenko/Reuters)

A woman works to create handmade Nepali Lokta paper in Kathmandu January 7, 2015. Lokta papers are made from the fibrous inner bark of Lokta bushes that are found over 5,000 metres above sea level. (Photo by Navesh Chitrakar/Reuters)

Chile's Javier Campillay drives past the burning car of Kazakhstan's Bauyrzhan Issabayev and Gabdulla Ashimov during the Dakar Rally 2014 Stage 2 from San Luis to San Rafael, on January 6, 2014. (Photo by Jean-Paul Pelissier/AFP Photo)

Throughout the course of the long war in Afghanistan, Coalition troops have relied on thousands of military working dogs to help keep them safe, and make their jobs easier. The dogs are trained to detect explosives, to find illegal drugs, to search for missing comrades, or target enemy combatants. Not only are they active on the front lines, but behind the lines they serve as therapy dogs, service dogs, and loyal companions. They also share the same risks as the ground troops, suffering injuries and sometimes death on the battlefields. Gathered here are images of these dogs and their handlers in Afghanistan and back home, from over the past several years, part of the ongoing series here on Afghanistan.

Canadian escape artist Dean Gunnarson attempts to work his way out of a straight jacket while hanging from a crane by a rope which is on fire during a Royal Melbourne Show preview at the Melbourne Showgrounds on September 23, 2011 in Melbourne, Australia. The Royal Melbourne Show officially kicks off tomorrow, and continues until October 4. (Photo by Mark Dadswell/Getty Images)