A bomb-sniffing black Labrador can mean the difference between life and death, for the US Marines patrolling the dusty footpaths of southern Afghanistan.
These "dogs of war" have saved countless lives and their record for finding hidden explosives has won them a loyal following.
"They are 98 percent accurate. We trust these dogs more than metal detectors and mine sweepers," says handler Corporal Andrew Guzman.
Trained to detect five kinds of threat, from military grade C-4 plastic explosive to common chemicals used by the Taliban to make improvised explosive devices (IEDs), the dogs play a vital role alongside their human comrades.
Bomb expert Sergeant Crush is all concentration as he leads a foot patrol by two squads of US Marines deployed to Afghanistan as part of Washington's fresh surge to end an eight-year insurgency by the Taliban.
His job along with Corporal Goodwin is to lead the men to safety through dusty footpaths and compounds where Taliban militants plant deadly bombs that have left many troops dead in recent months.
They are from a group of four Labradors, who are on average four years old and have all seen action in Iraq and Afghanistan.
"These dogs are great. They keep our Marines alive," says First Lieutenant Aaron MacLean, 2nd Platoon commander of the Marines 1st Battalion, 6th Regiment Charlie Company, to which the dog team is attached.
Crush suddenly goes on a swift bound, sniffing out a corner of a compound in the outskirts of a Taliban stronghold in Helmand province.
There is a quick change in his demeanour, his muscles tense up, he freezes, sticks out his tail and then lies down with his paws extended up front.
The area turned out to have been a former storage place for ammonium nitrate, a fertiliser compound recently banned by the government that the Taliban commonly use in making powerful homemade bombs.
"It's better safe than sorry," Guzman says.
Just days earlier two squads of Marines were ambushed and trapped in a compound. Two Marines died after stepping on the pressure plates of IEDs, just minutes before the dogs were to have cleared the area.
The force of the explosion threw the handlers and the dogs to the ground, but they quickly got up and resumed their jobs.
The dogs also provide an emotional crutch for young Marines facing death every day. They crowd around the dogs and play with them inside the camp. There are frequent questions about adopting them after the Labradors end their tour.
Lance Corporal George Grimm, the handler of Corporal Brooks, says most Marines feel safer with his bomb team leading the way.
Brooks, a three year-old Labrador with tan fur, has been deployed three times in Iraq and Afghanistan and has helped with the recovery of approximately 14 bombs and saved many lives.
One sniffer named Ringo gained a legendary reputation for having found as many as 30 daisy-chain landmines in Iraq, he says.
"Our life is in this boy's hands pretty much," says Grimm, a 19-year-old who has been Brooks' handler since late last year. Grimm grabs a rubber toy called a "konk" and lets Brooks nibble on it.
"They don't ask for much except to be taken cared of," he says.
Handlers say the US government spends huge amounts of money to train the dogs in a civilian-led programme contracted out by the defence department. Related article: Pressure mounts for Afghan solution
They begin training when they are puppies, and by the time they reach two and half years old, are ready to be deployed.
The bomb squad in Afghanistan prefer using pure-bred Labradors over sentry dogs such as German Shepherds because they are easier to train. Labradors are also hunting dogs who can pick up a scent as far as 500 metres (yards) away.
With the Taliban increasingly relying on IEDs to cripple the US advance, officials say up to 70 dogs are now on operation in southern Afghanistan alone, where the insurgency is festering.
More are expected to be deployed in the coming months, officials say.