The battle for the village of Mufti, in the Kurdistan region of Iraq, would have been simpler had it not been for Isis' sophisticated network of tunnels.
When Commander Ato Zibari led his Kurdish Peshmerga forces underground to rout out the last Isis fighters, one of them detonated a suicide vest rather than be captured alive.
"After he blew himself up, this man's phone began to ring," Zibari said. "One of my officers answered it and it was his wife. 'Where is Abu Mussab?' she asked. 'Is he in paradise?' The officer told her, 'No, he is a pile of ashes at my feet."'
More than 150 Isis (Islamic State) fighters have suffered a similar fate over the past week.
The Peshmerga have managed to push the terror group back west towards Mosul, the heart of its "caliphate" in Iraq, in a lightning offensive that has seen them recapture 80km of territory in the last six days.
Mufti, a 2000-year-old Christian village, had been controlled by Isis since the jihadists raised their black flag here in the northern summer of 2014. It was finally liberated last Wednesday with the help of air strikes from the US and its partners in the international anti-Isis coalition.
The commander said that British and American troops are heavily involved; advising on the front line and directing strikes from a nearby command centre.
Isis had bombed the bridge over the Khazir River to Mufti from the east. Today the only way to access the village from this side is over the Peshmerga's makeshift metal crossing.
Burnt-out cars line both sides of the main road, which has now become the front line.
"Look, Daesh," 23-year-old Peshmerga fighter Ali Hassan said as he handed over a pair of binoculars and pointed to a town not 1km away.
He took us to a house which had been hit by a US B52 bomber two days earlier. Inside one of the rooms was an opening to a labyrinth of tunnels built by Isis fighters trying to hide from the coalition planes overhead. Mounds of soil had been dumped in the house next door so as not to tip off surveillance drones.
We found empty pill cases, water bottles and huge piles of dates - the jihadists had stored enough food to spend several weeks underground.
The words "Dawla Islamiya", or Islamic State, were scrawled on the wall next to childish drawings of planes dropping bombs on fighters with Kalashnikovs.
The tunnel system was sophisticated and expertly constructed, reaching 3m-deep in some sections and half a kilometre long.
"They built the entrance inside a school - they knew it would be safe as the coalition would never bomb a school," said Lieutenant Saad Omar.
"From there it forks in three directions. One of the tunnels comes out behind our front line and on the first day of the operation Isis snipers shot at us from our own side. They had the advantage as they can see us, but we couldn't see them."
He said Isis "fought dirty" with tactics the Peshmerga had not come up against before.
"We are used to seeing bombs set off by a mobile phone. Now we are seeing Daesh set off one bomb and the sound of the explosion triggers 20 others around it like a necklace. That's how we lost four of our men this week."
He said when the jihadists are surrounded they detonate a vest "so they can become martyrs" rather than be captured or killed by "infidels".
At the entrance to one tunnel lay half a leg of a suicide bomber. The blast had been so powerful the rest of his body was nowhere to be found.
Most of Isis' fighters here had been young, poor Sunni Muslims from Mosul and the surrounding towns.
One who was captured gave his name as Ahmad Ibrahim and his age as 16. He told the Peshmerga he had been training to be a traffic policeman in the city when last week he was recruited by an Isis commander who said they were short of fighters. He was offered 60,000 Iraqi dinars ($80) and a gas canister to go and defend Mufti from the advancing Peshmerga.
The Islamist group is stretched thin as it battles simultaneous offensives near Mosul, Fallujah and the heart of its territory in neighbouring Syria.
Now we are seeing Daesh set off one bomb and the sound of the explosion triggers 20 others around it like a necklace
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In the current operation in northern Iraq, they are up against 5000 highly trained Peshmerga, including hundreds of female fighters. They know the land well and are disciplined, making them the most effective ground force against Isis.
They are supported from the air by the US-led coalition, but on the ground they have to rely on ageing Soviet-era equipment. Whatever weapons they take from Isis, they keep and use, one fighter told us.
"We are so thankful for the British and the Americans, as we could not have achieved what we have without them," said Zibari. But he said they will need more funding to keep up this level of fighting.
Mufti will only be a taste of what is to come 32km away in Mosul - the biggest city controlled by the terror group - where it has dug in over the last two years.
The Peshmerga estimate there are 9000 diehard Isis fighters in the city and that dislodging them will require at least 30,000 men, engaged in house-to-house fighting for up to six months.
Many of the residents who fled Mufti and other surrounding towns now liberated said they will not move back until Mosul has fallen. They are afraid that without cutting off the head of the snake, it will come back to bite them.
Hamid Abdel Majid, 50, said: "Only when we get a guarantee from the Iraqi Government, the Kurdish Regional Government and the UN that Isis is defeated will we return to our homes.
"We just hope there is something left to come home to."