It was once a secret base for Saddam Hussein's personal army but now Camp Taji hosts 400 members of the 1st Battalion, The Grenadier Guards as they train the Iraqi Army.
Four years ago IS (or Daesh) terrorists had swept across Syria and Iraq, killing and enslaving thousands of men and women. British troops were among the first to be sent to retrain the battered Iraqi Army as it tried to hold back so-called Islamic State from Baghdad.
In Saddam's time Camp Taji was a secret place. It hosted the the elite Republican Guard, Iraqi tanks were repaired there and chemical weapons were manufactured.
Signs of Camp Taji's past are clear to see.
Fifteen years after the US invasion, all that remains of Saddam Hussein’s military dream is a huge vehicle graveyard, filled with thousands of tanks and vehicles stretching as far as the eye can see.
The camp covers 13 square miles and is located northwest of Baghdad in an area called Tarmiya.
Today, it is one of the largest military bases in Iraq.
From 2003 onwards it was home to American forces before eventually being scaled down.
In the summer of 2014, Iraq's future looked more perilous when IS controlled swathes of the country and started closing in on Baghdad.
Despite an Iraqi Army of around 200,000 men, four divisions collapsed against the enemy.
Three years after leaving Iraq, British troops returned in a non-combat role - part of a coalition of nations sent in to urgently retrain Iraq’s army.
Inside, Camp Taji is a heavily fortified Green Zone, which is home to hundreds of coalition troops including the UK training team.
This is the ground element of the overall UK mission, Operation Shader - the British contribution to fighting Daesh in Iraq and Syria.
Around 1,300 British troops are involved in Op Shader , approximately 500 of them in Iraq.
Four months into a six-month tour the troops from 1st Battalion, The Grenadier Guards head a Battlegroup of around 400 troops providing training at bases across Iraq.
Lieutenant Colonel Piers Ashfield, Commanding Officer of The Grenadiers, said British troops have been providing "expertise" training.
"I think the key thing about British training has been the expertise it provided to those who were going through the experience of the frontline and counter IED, in particular, is an area where the Iraqi Army suffered significantly through expert emplacement from Daesh," he said.
The United Nations says 33,000 explosive devices have been removed from Mosul since it was liberated in July this year, including 450 suicide belts. Finding them all beneath an estimated eight million tonnes of rubble could take a decade.
Captain Nick Lawson, the Officer in charge of counter-IED training, explained some of the terror group's tactics: "The Daesh have left various IEDs - ranging from devices put in medical cabinets, to target people trying to help the wounded and building levellers.
"As soon as you walk into a building with a team it will just collapse on top of them.
"Some of the tactics being used are completely despicable."
Private Mohammed Sukran, from the Iraqi Army, described a moment his training was used when he came into contact with an IED:
"There were four of us and we went inside a house and someone found an IED in there.
"I'd had the training so I was called in to dispose of it. Daesh had hidden it underneath a copy of the Holy Quran, what we call an 'anti-lift' device."
Private Mohammed Sukran speaks about his encounter with an IED.
Lieutenant Colonel Nomas Mohammed Hussein, was in charge of a battalion near Fallujah four years ago.
He told Forces News that IS fighters came within 15 kilometres of the centre of Baghdad: "In 2014, when Daesh emerged we tried just to hold on to Baghdad.
"If this area had fallen into their hands, the whole city would have been lost.
"My division fought really hard around Baghdad, Abu Ghraib and Tarmiya to try and stop them getting in. It was a very hard mission.
"When you fight against people with this ideology, who are ready to die, it’s very hard to defeat them."
The Grenadiers are just the latest in a long line of units that have now served on Op Shader. For 70% of them, it's their first operational tour.
IN PICTURES: Thousands of military vehicles dating from Saddam Hussein's time as President of Iraq stand abandoned.
Since 2014, British soldiers have trained 75,000 members of the Iraqi security forces at Camp Taji and at other bases across the country.
Combat engineering is another key skill the British Army has been teaching in Iraq.
British personnel have been showing Iraqi engineers how to plant an explosive charge on a door or other entry point to allow troops to storm a building:
They have also practised moving vehicles over ditches or waterways in a battlefield scenario using a British bridge system.
The task is a test of teamwork and communication.
Brigadier General Hussein Azab Salman, Commander of the Military Engineering School, says the training is "hugely helpful" as they fight an enemy "without morals".
“Urban areas inside a city are the most difficult place for an army to fight," he explained.
"It’s hard to know who your enemy is amongst all the civilians and it’s not easy to target them because they hide amongst them.
"ISIS is an enemy without morals or any appreciation for human life.
"Since 2014, many of my soldiers have been fighting in Mosul and across Iraq and the training they’ve received here has been hugely helpful.
“I can’t give you an exact figure but we lost a number of engineers.
"This was an extremely hard battle – we fought in a city against a brutal enemy that tried every trick in the book to kill as many people – civilians and soldiers as possible.
"It wasn’t easy but in the end, we managed to defeat them."
Iraqi troops have also been taught the basics of battlefield first aid by the British Army and RAF medics.
In one instance, a Royal Navy medic shows Iraqi engineers how to apply a tourniquet - a device applied to wounds to stem blood loss.
In Afghanistan, these simple pieces of equipment saved the lives of countless British soldiers caught in IED blasts.
Iraq’s military fought hard to defeat Daesh – the outcome could have been very different without the support of western air power and Iranian-backed Shia militias.
IS sleeper cells are active in parts of Iraq.
Although question marks remain over Iraq's long-term security, Lieutenant Colonel Ashfield says he has faith in the "very capable" Iraqi forces.
"They retook Mosul, a particularly complex operation, in a very complex environment, much faster than anyone in the coalition had envisaged.
"During our tour, we've seen them conduct numerous autonomous operations, providing security for the Shia pilgrimage in Kabul for example, where they've very much done that on their own with great success.
"There's always room for improvement but they're a very capable fighting force."
Lieutenant Colonel Piers Ashfield on the "very capable" Iraqi forces.
Iraq's defeat of Daesh has come at a huge cost.
Figures vary, but some estimate up to 11,000 civilians died in the bloody battle for Mosul, either executed by Islamic State or inadvertently caught in coalition airstrikes.
The Iraqi military does not release casualty figures but the fight against IS is thought to have cost several thousand lives.
For Iraq’s army, pushed aside by IS just four years ago, it was a battle for pride as well as territory.
The training they have received at Camp Taji from the British Army and other nations has been a part of that victory.
But in the long term, defeating IS as a whole will take more than just military power.
In Iraq, it will also require solutions to some of the country’s deep-seated political and social problems.
The UK says British forces will be in Iraq until the job is done - what that means, of course, is another question but it could well be some time.