Visitors of the world's longest tree top walk between the trees of the Bavarian forest on November 6, 2009 in Neuschoenau, Germany. The path, 1300 meters long and in 8 to 25m height, winds up to an impressive tower with a height of 44 meters. The wooden construction is integrated into the forest and delivers a natural experience. (Photo by Miguel Villagran/Getty Images)

Workers at the World's Finest Chocolate company weigh what they hope will be a world record chocolate bar September 13, 2011 in Chicago, Illinois. The candy bar, weighing 12,190 pounds, standing nearly 3 feet high and measuring 21 feet long beat the previous record chocolate bar by more than a ton. (Photo by Scott Olson/Getty Images)

The Rainbow Warrior III, the newest ship of the enivornmental conservation organization Greenpeace, makes its way to port on the Elbe River on October 20, 2011 in Hamburg, Germany. The Rainbow Warrior III, 53 meters long, designed by Greenpeace and built in Poland and Germany, is a EUR 23 million project completed last week. (Photo by Sean Gallup/Getty Images)

Mike Branch helps customers shop for a Halloween masks at Fantasy Costumes on October 28, 2011 in Chicago, Illinois. The store, which had long lines at the registers at 4 AM this morning, is open around the clock through Halloween to help keep up with customer demand. Retailers nationwide are expecting record sales for Halloween merchandise this year with shoppers spending close to $7 billion dollars to celebrate the holiday. (Photo by Scott Olson/Getty Images)

People line up to buy toilet paper and baby diapers at a supermarket in downtown Caracas January 19, 2015. There's a booming new profession in Venezuela: standing in line. The job usually involves starting before dawn, enduring long hours under the Caribbean sun, dodging or bribing police, and then selling a coveted spot at the front of huge shopping lines. As Venezuela's ailing economy spawns unprecedented shortages of basic goods, panic-buying and a rush to snap up subsidized food, demand is high and the pay is reasonable. (Photo by Jorge Silva/Reuters)

A woman wears roller skates with lights on the bottom at Rich City Skate in Richton Park, Illinois, January 12, 2015. A handful of decades-old skating venues put Chicago at the center of a vibrant African-American subculture of urban roller skate dancing that stretches from Atlanta to Detroit and from Los Angeles to New York. While mainstream roller skating has been on a long decline, a new generation of skaters travel a circuit of rinks around the country to compete and show off their moves. (Photo by Jim Young/Reuters)

“A British photographer has captured incredible images of Italys most beautiful derelict buildings – by sneaking into abandoned structures. The stunning shots of hospitals, churchs and deserted buildings show abandoned beds, overgrown arches and staggering staircases. Gaz Mather, 40, is a dedicated urban explorer who takes stunning photographs of deserted buildings – documenting their haunting decay. Gaz from Manchester spent a long weekend touring deserted buildings in the Northern region of Italy”. – Caters News. Photo: Abandoned Villa. (Photo by Gaz Mather/Cater News)

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.