The 27th Annual Tompkins Square Halloween Dog Parade was held on October 21, 2017. Thousands of costumed canines and spectators marched on Tompkins Square Park to participate in the countrys largest Halloween. (Photo by Erik McGregor/Pacific Press/LightRocket via Getty Images)

Melissa Stewart's team competes in the official restart of the Iditarod, a nearly 1,000 mile (1,610 km) sled dog race across the Alaskan wilderness, in Fairbanks, Alaska, U.S. March 6, 2017. (Photo by Nathaniel Wilder/Reuters)

A man cuts dog meat at a dog meat restaurant ahead of local dog meat festival in Yulin, Guangxi Zhuang Autonomous Region, China on June 21, 2018. The festival in the southwestern town of Yulin has long drawn international criticism, with thousands of dogs traditionally being killed during the event. (Photo by Tyrone Siu/Reuters)

Disabled dogs outfitted with wheelchairs walk at an animal rescue center on July 12, 2008 in Chengdu of Sichuan Province, China. The center has adopted over 100 stray dogs and cats from quake-struck areas. Those who were hurt or disabled are outfitted with a cart to help support they're body and make them mobile. (Photo by China Photos/Getty Images)

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.

A police officer jump ropes with a police dog at a police dog training base on July 11, 2011 in Beijing, China. The Police Dog Training Base was opened to a media visit to show the dogs skills to the public. (Photo by ChinaFotoPress/Getty Images)

“Photographer Seth Casteel has definitely taken animal photography to new heights – or depths – with his hilarious photos of dogs chasing balls underwater. Casteel, who, naturally, has two dogs of his own (a mini Labradoodle and a Norwich terrier), said that he's drawn to underwater dog photography because the photos show a side of dogs that people may have never seen before”.

Photo: Seth Casteel Underwater Dog Pictures (Photo by Seth Casteel)