President Woodrow Wilson speaks on telephone. Woodrow Wilson was the 28th U.S. President serving from 1913 – 1921. (Photo by Corbis)

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.

Unwanted phones recreated as interactive birds, part of “Escape III” by Anthony Goh and Neil Mendoza seen on display at the Barbican's Digital Revolution exhibition on July 2, 2014 in London, England. The exhibition brings together artists, designers, film makers, musicians and architects who push the boundaries of creativity that digitial technology can offer, and runs from July 3 until September 14, 2014. (Photo by Matthew Lloyd/Getty Images for Barbican Art Gallery)

Relatives of a missing person scuffle with police officers on the bank of the Yangtze River, near Jingjiang, Jiangsu province January 17, 2015. A search and rescue operation was still underway after the boat capsized on January 15, leaving 22 people missing, including foreigners. (Photo by Aly Song/Reuters)

Playboy Bunny, Penny (surname not given), is helped into her costume as she prepares herself before starting work at the Playboy Club on July 26, 2016 in London, England. The Playboy Club London is celebrating its 50th anniversary this year and will mark the event with a “Touch of Gold” party on July 29. (Photo by Carl Court/Getty Images)

2016 Rio Olympics, Swimming, Preliminary, Men's 100m Backstroke, Heats, Olympic Aquatics Stadium, Rio de Janeiro, Brazil on August 7 2016. Christopher Reid (RSA) of South Africa competes. (Photo by Dominic Ebenbichler/Reuters)

Indian school children wearing traditional Punjabi attire sit as they take part in the full and final dress rehearsal for India's Independence Day parade and celebrations in Amritsar, India, 13 August 2016. India's 70th Independence Day will be celebrated on 15 August, to commemorate its independence from British rule and its birth as a sovereign nation on that day in 1947. (Photo by Raminder Pal Singh/EPA)

Tanzania, 1964. A touching moment between primatologist and National Geographic grantee Jane Goodall and young chimpanzee Flint at Tanzania's Gombe Stream Reserve. (Photo by Hugo van Lawick via National Geographic)