And while there were hundreds of human heroes in the days following the September 11 attacks in the United States, there were plenty of four-legged heroes too -- the dogs who searched for survivors and bodies among the rubble of buildings and planes. Ten years later, the 9/11 dogs that are still alive are long retired, but there's a new generation coming up behind them.

Meet "Red" -- a 12 year-old Labrador who searched the rubble of the Pentagon after the September 11 attack. She was just 18 months old at that time and only recently certified as a rescue dog, a rookie among more veteran canines. Red searched the debris with an energy that surprised even her handler.

Red, 12, from Annapolis, Maryland, went with Heather Roche to the Pentagon from September 16 until the 27 as part of the Bay Area Recovery Canines.

Heather Roche, rescue dog trainer, said, "I never thought she would be a successful search dog and actually at six months old I found a home for her and had found another dog. I thought she's never going to -- her personality is not what is needed for a working dog. And then, no matter what I asked her to do -- whether it was climbing up things, going somewhere I stayed far away, ladders, you name it -- she did it every single time and she did it perfectly,"

For weeks, Red navigated the hazards of the rubble piles amid the clatter and chaos of the days following 9/11. After Red discovered dozens of bodies, Heather Roche was sure that, among all the rescue dogs working the pile, Red was one of the best.

Heather Roche, rescue dog trainer, said, "They worked so hard and it was so hot and we were on a day shift, so it melted all of us. Just the work basically --, 12 hour shifts out in the sun. By the time we were done every day, they slept hard. They were sleeping like rocks, but they were willing the next morning. They were rejuvenated and pulling on the leash to go back to work,"

After retiring, Red still tags along on some search missions. But just as the human rescue teams continue to suffer from their work at the World Trade Center, it also took its toll on the dogs.

Heather Roche, rescue dog trainer, said, "You know, a major event like that, I appreciate her more. I've had a lot of older dogs that I was probably a little more frustrated with them than I should have been when they got older. With her, you know she's earned the right to do anything she wants."

Ten years have passed, and Red is now retired. But Red still has that same love of the search. For the 10th anniversary of 9-11, she and other search dogs deserve to be honored and respected by human beings.

Searching for survivors: The dogs worked around the clock in the vain hope of finding anyone still alive at the World Trade Center site.

Guinness, 15, from Highland, California, started work at the site with Sheila McKee on the morning of September 13 and was deployed at the site for 11 days.