PETA (People for the Ethical Treatment of Animals) activists wear crocodile masks during a demonstration against the use of crocodile skins ahead of Milan's Fashion Week, in Milan's Duomo Square, Italy, Tuesday, February 21, 2017. Milan Fashion Week opens Wednesday. (Photo by Antonio Calanni/AP Photo)

Members of the Guard of Honor of the Presidential Regiment from Russia perform during the “Spasskaya Tower” international military music festival at Moscow's Red Square, Russia, September 10, 2015. The festival runs until 13 Sepember. (Photo by Maxim Shemetov/Reuters)

A workman smooths out the gravel near the base of British artist Alex Chinneck' latest sculpture “A bullet from a shooting star” on the Greenwich Peninsula in London on September 17, 2015. The 35-metre tall, upside-down electricity pylon overlooks the Canary Wharf financial district. (Photo by Leon Neal/AFP Photo)

In this December 29, 2004 file photo, Kusol Wetchakul offers prayers for the soul of his sister, at dawn along the beach near Khao Lak, Thailand. Wetchakul's sister was swept out to sea and believed drowned as she sold goods to tourists on the popular tourist beach just north of Phuket. Friday marks the 10th anniversary of one of the deadliest natural disasters in world history: a tsunami, triggered by a massive earthquake off the Indonesian coast, leaving more than 230,000 people dead in 14 countries and causing about $10 billion in damage. (Photo by David Longstreath/AP Photo)

Children play on top of an old plane's fuselage at a dump site in Paranaque city, Metro Manila, Philippines January 21, 2017. (Photo by Ezra Acayan/Reuters)

A handout picture provided by Global newsroom of Czech Martin Sonka (C) leading Nigel Lamb (top) of Great Britain and Yoshihide Muroya of Japan (down) along the Mount Fuji prior the third stage of the Red Bull Air Race World Championship in Chiba, Japan on June 1, 2016. (Photo by Predrag Vockovic/EPA/Global Newsroom)

Old Heidelberg, Dog with Pipe, 1905. (Photo by Detroit Publishing Company)

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.