Women take a selfie next to a police officer as they take part in New Year's Eve celebrations in the Bund, in Shanghai, China December 31, 2016. (Photo by Aly Song/Reuters)

A woman poses with her tattoo during the Shanghai Tattoo Extreme & Body Art Expo 2017 in Shanghai, China September 2, 2017. (Photo by Aly Song/Reuters)

In this timed-exposure night photo taken early on February 12, 2017, Mount Sinabung volcano spews reddish smoke and ash, as seen from the Karo district in North Sumatra province. Activity levels have increased in the past week, with Sinabung shooting hot ash clouds into the sky dozens of times, according to the local volcano monitoring agency. (Photo by AFP Photo/Stringer)

Clearing skies await a tripod-toting photographer looking for a spot to capture the early-morning light at Portland Head Light, Thursday, January 17, 2013, in Cape Elizabeth, Maine. (Photo by Robert F. Bukaty/AP Photo)

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)

Actors Aubrey Plaza and Matthew Gray Gubler pose for a portrait during the 2014 Sundance Film Festival at the Getty Images Portrait Studio at the Village At The Lift on January 19, 2014 in Park City, Utah. (Photo by Larry Busacca/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.

Members of the Times Square Alliance snow clearing team take a photo on a snowbank at Times Square in the Manhattan borough of New York January 23, 2016. A winter storm dumped nearly 2 feet (58 cm) of snow on the suburbs of Washington, D.C., on Saturday before moving on to Philadelphia and New York, paralyzing road, rail and airline travel along the U.S. East Coast. (Photo by Shannon Stapleton/Reuters)