“A monowheel is a one-wheeled single-track vehicle similar to a unicycle. However, instead of sitting above the wheel, the rider sits either within it or next to it. The wheel is a ring, usually driven by smaller wheels pressing against its inner rim. Most are single-passenger vehicles, though multi-passenger models have been built.

Pedal-powered monowheels were built in the late 19th century; most built in the 20th century have been motorized. Some modern builders refer to these vehicles as monocycles, though that term is also sometimes used to describe motorized unicycles. Today, monowheels are generally built and used for fun and entertainment purposes, though from the 1860s through to the 1930s, they were proposed for use as serious transportation”. – Wikipedia

Photo: Cycle inventor Kerry McLean poses for the photographer 2000 in Walled Lake, Michigan. The “Monocycle” is equipped with a 40-horsepower engine, 4ft tire and is expected to reach speeds upwards of 100 mph. (Photo by Bill Pugliano/Liaison)

Models Lara Stone, Doutzen Kroes, CEO of l'Oreal Cyril Chapuy, Actress Eva Longoria, Models Karlie Kloss and Isabeli Fontana attend amfAR's 22nd Cinema Against AIDS Gala, Presented By Bold Films And Harry Winston at Hotel du Cap-Eden-Roc on May 21, 2015 in Cap d'Antibes, France. (Photo by Pascal Le Segretain/amfAR15/WireImage)

A giant storm cloud can be seen in the sky above swimmers near Mollymook Beach, south of Sydney, March 5, 2014. (Photo by David Gray/Reuters)

When Ed Templeton was a young skateboarder in California, he took Polaroids of his friends smoking at their local park. Those pictures in 1994 were the start of a lifelong habit – Templeton has been capturing youngsters all over the world experimenting with cigarettes ever since. Here: Santiago, Chile, 2002. (Photo by Ed Templeton/Robert & Tilton Gallery, Culver City)

(L-R) Leigh-Anne Pinnock, Jesy Nelson, Perrie Edwards and Jade Thirlwall of Little Mix attend the KISS FM Haunted House Party at SSE Arena on October 29, 2015 in London, England. (Photo by Dave J. Hogan/Dave J. Hogan/Getty Images)

North Korean soldiers wave along the Yalu River, near the North Korean town of Sinuiju, opposite to the Chinese border city of Dandong October 7, 2014. (Photo by Jacky Chen/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.