During his time in Ethiopia, New York-based art director and photographer Diego Arroyo spent time with the Hamar, Mursi, Dassanech, and Arbore Tribes. They, along with several others tribes, make up the 200,000 people situated in Africa’s Great Rift Valley. The people of the Omo Valley are still primarily herders and farmers, living an isolated and simple life. While they have yet to be truly touched by globalization, they could soon disappear. Their way of life is being threatened by a massive hydroelectric dam. (Photo by Diego Arroyo)

Pfc. Sebastian Rodriguez, machine gunner, Weapons Platoon, Lima Company, 3rd Battalion, 3rd Marine Regiment, Marine Rotational Force – Darwin, fires an M240 machine gun during a night squad-attack exercise, here, May 22, 2013. (Photo by Sgt. Sarah Fiocco/U.S. Marines)

Trevor Olson, from Minnesota, dressed as the character “Joker”, poses for a photograph at New York's Comic Con convention, October 9, 2014, in New York City. The event draws thousands of costumed fans, panels of pop culture luminaries and features a sprawling floor of vendors in a space equivalent to more than three football fields in Javits Center. (Photo by Shannon Stapleton/Reuters)

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.

Model Heide Lindgren attends Heidi Klum's 12th annual Halloween party at the PH-D Rooftop Lounge at Dream Downtown on October 31, 2011 in New York City. (Photo by Jemal Countess/Getty Images)

In this handout artists impression provided by the Russia 2018 Organising Commitee, the Rostov on Don Stadium is shown as proposed and presented as part of the Russia 2018 World Cup bid, on September 29, 2011 in Russia. (Illustration by Russia 2018 via Getty Images)

A tufted puffin is seen in Kamchatka Territory, Russia on July 17, 2018. (Photo by Yuri Smityuk/TASS)