Chacha, the male chimp, screams at a worker in Sendai, northern Japan, Thursday, April 14, 2016 after fleeing from a zoo. The chimpangzee tried desperately to avoid being captured by climbing an electric pole. Chacha was on the loose nearly two hours Thursday after it disappeared from the Yagiyama Zoological Park in Sendai, the city that's hosting finance ministers from the Group of Seven industrialized nations in May. (Photo by Kyodo News via AP Photo)

In this Wednesday, August 20, 2014 photo released by Red Bull, Maikel Melero of Spain warms up prior to the fifth stage of the Red Bull X-Fighters World Tour in the South African savanna of Pretoria, South Africa. (Photo by Joerg Mitter/AP Photo/Red Bull)

Two sheep fight in a competition in Zhangjiakou, Hebei province, China on August 1, 2017. (Photo by Reuters/China Stringer Network)

A woman dressed in a traditional Ukrainian embroidered shirt holds her cat as she take part in an embroidered shirt parade in central Kiev, Ukraine, May 27, 2017. (Photo by Gleb Garanich/Reuters)

“I was doing some event shooting for Bar One's Beer And Wine garden. I was working with these two ladies when all of a sudden I hear an "excuse me” and I see dude step into the frame right when I pressed the shutter button!” (Photo by 17thletter Photography)

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.

Arctic treasure by Sergey Gorshkov (Russia). An arctic fox carries its egg trophy from a raid on a snow goose nest and heads for a suitable burial spot. Finalist 2017, Animal Portraits. (Photo by Sergey Gorshkov/2017 Wildlife Photographer of the Year)

Hidden Britain category winner. Garden Spider by Alan Smith from Reading, Berkshire. (Photo by Alan Smith/British Wildlife Photography Awards/PA Wire Press Association)