US military dog helped in Osama Bin Laden compound raid
We'll probably never know much about the elite Navy Seal team that killed Osama Bin Laden.
Training, tactics - almost everything about them is top secret.
But there's been a string of rumours and reports about one member of the team in particular. One with four legs. And really big teeth.
At US army base Fort Drum in New York, Sergeant Justin Martin and his dog Kay are preparing to go to Afghanistan in two weeks.
Today though, they face a gruelling day of tests that could cause them serious problems if they fail.
"I'm going through certification," says Sergeant Martin.
"It tests my dog's ability to find odours, as well as my own ability to handle the dog."
It's stressful, not just for Sergeant Martin, but also for his kennel master at Fort Drum, Sergeant Anthony Bostwick.
"It's a nerve-wracking day for me," he says. "If any of the dog teams fail certification, it's a direct failure of the kennel master."
Kay is a six-year-old Belgian Malinois. He is a PED dog, which stands for patrol and explosives detection.
He is trained both to attack on demand and to sniff out bomb-making material.
Sergeant Bostwick says the dog used in the Bin Laden raid was most likely a PED, and therefore either a Malinois like Kay, or a German Shepherd.
It's reported that the handler rappelled, or abseiled, out of a hovering helicopter on ropes, with his dog strapped to his chest.
"All that would be normal training for any dog team going through helicopter training," says Sergeant Bostwick.
Lieutenant Colonel Carl Packer commands the 91st Military Police Battalion at Fort Drum.
"These dogs combine aggressive training and explosives detection," he says.
"Those unique capabilities would have been a mission plus for the Seal team going in to capture Bin Laden."
A powerful dog like Kay, trained to be ferocious at the end of a long leash, would have spread panic and confusion for anyone in Bin Laden's compound.
He also would have been able to chase and catch anyone trying to escape in the opening moments of the raid.
A Malinois or a German Shepherd runs twice as fast as a human.
Once it latches on to its target it won't let go until it gets a fresh command from its handler.
"Our dogs are superbly trained," said Lieutenant Colonel Packer.
"If they're being aggressive, it's because the handler wants them to be aggressive," he added.
But not all the dogs at Fort Drum are trained to be fierce.
Iiken is a black Labrador. He's been taught to run ahead of his handler and sniff out roadside bombs.
Dogs like Iiken have been used for years to find improvised Taliban explosive devices (IEDs).
General David Petraeus, America's top soldier in Afghanistan said last year, said: "The capability they bring to the fight cannot be replicated by man or machine."
It's understood that about 2,700 dogs are employed by the US military.
In the UK, the number is more like 1,000, if you include military police and guard dogs.