This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

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.

VIETNAM: A Vietnamese woman, wearing the traditional “ao dai” long dress, poses for photos along peach blossom flowers ahead of the Vietnamese “Tet” (Lunar New Year festival), in a field in Hanoi, Vietnam, February 2, 2016. (Photo by Reuters/Kham)

When wedding photographer Katie Yeaton saw that one of her dogs had white fur and the other had black-and-white fur, she did what only a wedding photographer could do: she threw them a backyard wedding complete with professional photography to remember the day. (Photo by Katie Yeaton)

“DC3 Wreck”. A capture of a US military DC3 plane wreck at the southern black beach in Iceland. Photo location: Iceland. (Photo and caption by Naian Feng/National Geographic Photo Contest)

Macro or Micro? Scientists’ pictures baffle our sense of scale. It began when Stephen Young, a geography professor at Salem State University in Massachusetts, tricked his biologist colleague Paul Kelly into thinking a satellite image was one of his electron microscope scans. Can you guess whether they are close-up or very far away? (Photo by Paul Kelly)

Once upon a time a girl named Laura lived in Columbus, Ohio. She had a nice family, and got good grades, but it was always rainy and cold in Columbus, which was neither nice nor good, so she wore lots of sweaters and turned the heat up when her dad wasn’t looking.

“A Cornish pasty, sometimes known as a pastie or British pasty in the United States, is a filled pastry case, associated in particular with Cornwall in Great Britain. It is made by placing the uncooked filling on a flat pastry circle, and folding it to wrap the filling, crimping the edge at the side or top to form a seal. The result is a raised semicircular package”. – Wikipedia

Photo: Cornish students (R) Nina Brooke, 21 and (L) Bonnie Mably, 20, laugh as they pose for a photograph as they try a Cornish pasty that has been baked as part of the World Cornish Pasty Championships at The Eden Project on March 3, 2012 in St Austell, England. (Photo by Matt Cardy/Getty Images)