CLEVELAND -- From playmate to protector, dogs are known as man's best friend.
But for a group of elite dogs, they're also taking on the job of serving as a Marine.
Goodwin is not your typical Marine. As a bomb-sniffing dog, Goodwin has done 4 tours of duty in Afghanistan. He's sniffed out 15 explosive devices, saving dozens of lives.
Photos: Dogs of the Marine Corps
Lance Corporal Stephen Baccari says, "It's definitely nerve wracking when he lays down in front of a vehicle and you think- this could be it."
It takes weeks of training before these Marines are ready for combat.
One way Marines train their dogs is to learn how to search for the main ingredient in bombs -- ammonium nitrate. But training aside, the most important tool is trust.
Baccari explains, "That's your brother right there, that's your best friend. He's with you every day. When you're overseas, he lives in your tent or they live near you in a kennel that you make. You feed them every day. You wake up next to them."
The relationship between human Marine and dog Marine is complex.
Baccari stresses, "It's not a pet, it's a Marine. And you have to remember that. If you make him a pet, he'll lose his obedience."
But there's also an underlying sense of compatibility.
Baccari says, "We sat down and wrote our personality and they try to match your personality with the dogs and it's amazing how well they do that because people started looking like their dog, the way they acted."
It's a relationship that is tested time and time again with lives on the line, a bond that these fellow Marines will share forever.
Only Labrador Retrievers are used to sniff out bombs. It's something this hunting breed is very skilled at.
There are hundreds of dogs currently serving as a Marine. To date, these dogs have found 100 explosive devices.
Know that 18 dogs have died in combat since 2008.