A rainbow is seen near a cloud south of Corvallis, Ore., Monday, May 19, 2014. (Photo by Andy Cripe/AP Photo/The Corvallis Gazette-Times)

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.

Tank crew standing in front of M-4 tank, Ft. Knox, Kentucky, June, 1942. (Alfred Palmer/OWI/LOC)

“I’d come to the Altai Mountains on an Adventure Sherpas tour. Our group of 12 was made up mostly of Minnesotans who’d left warm weather and falling leaves for frosty Mongolia. We’d come to sleep in cozy ger tents, the traditional yurt abode of the Mongolian steppe; sip mare’s milk tea; climb mountain glaciers; ride horses to an ancient battle site, and attend the annual Eagle Hunting Festival in Ölgiy...”. – Kathryn Kysar via The Star Tribune. Here: hunter Berek and his eagle outside his home. (Photo by Brad Ruoho/The Star Tribune)

A new book of photos by legendary photographer Weegee shows what industrialized, pre-gentrified New York looked like in the mid-20th century, before the city was crammed with towers and billboards. Here: this combination shows the 1945 photo “Derelict sleeping on the sidewalk outside police headquarters” by Weegee, provided by the International Center of Photography in New York, and a woman walking on the same spot on Wednesday, March 18, 2015. (Photo by AP Photo/Copyright Weegee/The International Center of Photography, Mark Lennihan)

In this two photo combination picture, the Eiffel Tower with its usual lighting at left, and after the lighting was switched off at right, at the occasion of the Earth Hour, in Paris, France, Saturday March 28, 2015. This Saturday, 28 March 8:30 p.m. local time, individuals, businesses, cities and landmarks around the world are switching off their lights for one hour to focus attention on climate change. (Photo by Remy de la Mauviniere/AP Photo)

Russian soldiers write home while serving on the Eastern Front during World War I, circa 1915. (Photo by Hulton Archive/Getty Images)

Clown/comedian/filmmaker Pierre Etaix attends The Academy Of Motion Picture Arts And Sciences' Presents “Pierre Etaix: The Laughter Returns” at AMPAS Samuel Goldwyn Theater on November 16, 2011 in Beverly Hills, California. (Photo by Valerie Macon/Getty Images)