A visitor holds up her toy bunny to the aquarium glass in front of Aurora the Russian polar bear at the Sao Paulo Aquarium in Sao Paulo, Brazil, Thursday, April 16, 2015. (Photo by Andre Penner/AP Photo)

Sikh devotee take part in Nagar Keertan procession on the occasion of Guru Gobind Singh birth anniversary in Allahabad, India on December 29, 2016. Guru Gobind Singh, born Gobind Rai (1666 – 1708), was the 10th Sikh Guru, a spiritual master, warrior, poet and philosopher. When his father, Guru Tegh Bahadur, was beheaded for refusing to convert to Islam, Guru Gobind Singh was formally installed as the leader of the Sikhs at age nine, becoming the last of the living Sikh Gurus. (Photo by Prabhat Kumar Verma/Pacific Press via ZUMA Wire/Rex Features/Shutterstock)

A horse- drawn carriage rides along the race course through the Thuringian Forest in Oberhof, Germany, 05 January 2017. Winter found its way to Saxony, Saxony- Anhalt, and Thuringia. In some regions it can get as low as negative 20 degrees overnight. (Photo by Martin Schutt/Zentralbild/DPA)

People try out the XIM 17 vehicle interior concept unveiled by Yanfeng Automotive Interiors during the North American International Auto Show in Detroit, Michigan, U.S., January 10, 2017. (Photo by Brendan McDermid/Reuters)

A boy rides on a snow wagon towed by a robot dressed as a Teddy bear, which only moves forward by moving its legs, during the Ice and snow carnival at Taoranting park in Beijing February 9, 2015. (Photo by Kim Kyung-Hoon/Reuters)

A migrant carries his belongings as he arrives at the Beijing railway station to catch a train in Beijing, Friday, February 13, 2015. (Photo by Andy Wong/AP Photo)

A hot air balloon in tortoise shape flies in the air during the Tazaungdaing air balloon festival in Pyin Oo Lwin, Myanmar, 25 November 2015. During the festival, hot air balloons made of multicolored papers and hung with paper lanterns, fireworks and fire sticks are exploded in mid-air. (Photo by Hein Htet/EPA)

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.