Two carnival revellers masquerade as Leonardo da Vinci's painting “Mona Lisa” pose in St. Mark's Square in Venice, Italy, Sunday, January 31, 2016. Carnival-goers in Venice are being asked by police to momentarily lift their masks as part of new anti-terrorism measures for the annual festivities. (Photo by Domenico Stinellis/AP 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.

A combination photo shows Fata Kovacevic reacting near her flood-damaged house during floods May 20, 2014 (top) and the same place after floods October 8, 2014 in Topcic Polje. (Photo by Dado Ruvic/Reuters)

The 100-metre (300-foot), sword-wielding statue of “The Motherland” is seen in the National Museum of the History of the Great Patriotic War in Kiev March 17, 2014. On a blustery day on the banks of the Dnieper, the statue of “The Motherland”, a Soviet hammer and sickle on her shield, towered overhead, a reminder of the common cause Ukrainians and Russians died for side by side in their millions in World War Two and which Russian President Vladimir Putin thinks Ukraine has betrayed by turning to “fascism” and the West. (Photo by Konstantin Grishin/Reuters)

A woman poses for a photographer (not pictured) as a man sits next to her in downtown Catania, Italy April 20, 2016. (Photo by Tony Gentile/Reuters)

A girl types on a computer as she demonstrates the interior of the new Volvo S90 during the Auto China 2016 auto show in Beijing April 25, 2016. (Photo by Damir Sagolj/Reuters)

Boys walk near a damaged building in the rebel held besieged city of Douma, in the eastern Damascus suburb of Ghouta, Syria December 30, 2016. (Photo by Bassam Khabieh/Reuters)

Fireworks explode over the Kremlin in Red Square which was blocked by police during New Year celebrations in Moscow, Russia, Sunday, January 1, 2017. New Year's Eve is Russia's major gift-giving holiday, and big Russian cities were awash in festive lights and decorations. (Photo by Alexander Zemlianichenko Jr./AP Photo)