It was like a scene from a Mad Max movie. As dawn broke on Thursday, hundreds of armoured vehicles, bulldozers and pick-up trucks, some with improvised bulletproof steel plates bolted on their sides, trundled in convoy across the parched desert plain.

They moved slowly, cautiously, wary of the inevitable roadside bombs on the dusty track ahead and the appearance of suicide bombers hurtling trucks laden with tons of explosives in their direction.

On board the convoy’s motley assortment of vehicles were thousands of Kurdish Peshmerga fighters, tasked with opening up the biggest military offensive yet against Islamic State (IS) cadres who have held Iraq’s second largest city Mosul for the past two years.

“Today we will kill Daesh, the time has come to push them from our country and make our people free,” says Ferhat, a young Peshmerga fighter adopting the commonly used Arabic acronym here for the IS jihadists. He is carrying a rocket-propelled grenade launcher (RPG) over his shoulder and in a backpack the khaki-coloured pointed heads of the rockets he uses as ammunition stick out like crayons in a child’s pencil case.

Ferhat smiles broadly, but the onerous task he and his comrades face is instantly brought home by yet another thunderous boom from the direction of the route ahead. Within seconds the black smoke rising from the explosion joins other plumes billowing into a broad dark blanket hovering in the direction of Mosul.

“These days will be difficult for us, but for Daesh these are their final days,” Ferhat assures me, still grinning as he clambers into a pick up truck crammed with other Peshmerga.

As the convoy carrying the first wave of Kurdish fighters advances, hundreds more Peshmerga stand watching from the top of a huge sand bank that up until now had marked the position of the existing frontline. Strung out in single file along the narrow ridge of the sand bank, weapons slung over their shoulders and some peering through binoculars, they stand silhouetted against the dawn sky. All of them will be moving towards Mosul in an assault aimed at retaking a string of villages along the route where IS have been dug in for some considerable time.

It was 11 o’clock on Wednesday night when myself and a journalist colleague received a call from the Kurdish authorities advising us to make the three-hour drive north to a Peshmerga frontline base near Nawaran. Though no other details were given, we sensed instantly something major was imminent. On our arrival even in the blackness it quickly became apparent that masses of fighters were gathering.

Sitting in our vehicles through the bitterly cold night and unable to sleep in anticipation of the following morning’s attack, we listened as US-led coalition aircraft circled overhead before “softening up” IS resistance with repeated airstrikes, causing thudding explosions to reverberate in the distance.

As the sun rose, the scale of the impending operation became apparent. The Peshmerga would advance from three frontlines moving forward from the villages of Bashiqa, Tel Iskuf and Nawaran that sits only nine miles north of Mosul.

This was to be the biggest operation since the start last Monday of the push on Mosul in which some 18,000 Iraqi troops, 10,000 Peshmerga and a few thousand Iraqi federal police have been deployed, constituting the biggest operation by Iraqi forces since the 2003 US-led invasion.

For the Peshmerga on Thursday, their target was a further sprawling series of villages to the north and north-east of Mosul still under IS control. On the dry, cracked desert soil near Tel Iskuf, I watched as a group of Peshmerga performed the traditional Kurdish dance linking arms and shuffling one way then the other as the first wave of vehicles rolled out.

As some of the vehicles waited their turn to move off, one of the drivers, a young man called Hassan, told me that he was from Mosul but had fled with his family when IS overran the city in 2014, turning it into the de-facto capital of their Islamic caliphate.

“My uncle was beheaded because he was wearing this,” Hassan tells me pointing to his own uniform implying that his uncle was also a Peshmerga. He says the Kurdish forces should be allowed to enter Mosul along with the Iraqi Army, a contentious issue among some political leaders in Baghdad who are suspicious of the Kurds’ own territorial ambitions. “Not all Arabs belong to Daesh,” Hassan says emphasising that Mosul’s local Arab population have nothing to fear by way of retribution from the Kurds. “We are not like the Popular Mobilisation Units (PMU), we would protect the innocent women and children,” he insists, referring to the Iraqi Shiite militia which has established a reputation for taking revenge against Sunni Muslims in other towns and cities in Iraq retaken from IS.

Hassan says that he is still in contact with friends in Mosul, a huge risk for them as IS steps up its brutal repression, executing in the most horrific way anyone inside the city communicating with those outside. Like Ferhat before him Hassan too admits that IS will present a formidable challenge.

“We don’t have much in the way of advanced weapons and equipment, but we do have our determination,” he reminded me by way of a parting remark before being ushered into his armoured pick-up truck by fellow fighters of his unit keen to get under way.

No sooner had Hassan’s vehicle moved off however than a peculiar buzzing sound could be heard just a few hundred feet in the sky above us. Looking up along with hundreds of Peshmerga, we saw what was a small IS surveillance drone.

Leaving our own driver, Bekus, in what we thought was the comparative safety of the Peshmerga main redoubt, fearful of putting him unnecessarily in harms way by accompanying us forward, myself and a colleague managed to hitch a lift along with the Peshmerga convoy.

Only later that day on our return to the position, did we find out that the drone had again flown over the same Kurdish frontline, this time to be blasted from the sky by a mass fusillade of small arms fire from the Peshmerga waiting to join the second wave of the operation.

Our earlier offer of a lift along with the Peshmerga convoy came from a reporter and cameraman from the Iraqi television political channel Rega, a media outlet widely associated with the Communist Party of Kurdistan (CPK). Both journalists as well as their driver and bodyguard were from the town of Sinjar and belonged to the ethnic and religious minority Yazidi community which has suffered some of the worst and most barbaric oppression under IS rule.

Slowly, but steadily, we moved forward, the Peshmerga ahead of us engaging with IS resistance as they met it. Some of the fighters at the head of the column carried sophisticated portable shoulder-held anti-tank missile launchers to destroy any incoming IS suicide bombers in trucks packed with explosives.

“We should stay close to the convoy, IS are still all around here,” one of the Rega journalists warned, as we passed piles of used shell cases and other fresh detritus of battle scattered in the dirt alongside the track. At each strategic position of the road, often on high ground overlooking villages, the Peshmerga were busy consolidating their territorial gains by deploying fighters, setting up defensive positions and constructing sand barriers using the earthmoving vehicles accompanying them to stop the suicide truck bombers from accessing tracks coming in the direction of the Kurdish advance.

At one position just behind a freshly constructed sand bank a few yards from where we crouched, I watched two Peshmerga directing a JCB driver to cover something on the ground with earth.

“What is it, corpses?” I enquired of one fighter. “No, just an unexploded mortar bomb,” came his matter-of-fact reply despite the vibration and noise of the earthmover that might have detonated the weapon. By now the Kurdish advance had been slowed by stiff resistance from IS fighters dug in around the town of Barima and the village of Dere.

“Most likely they are using tunnels to move around,” one Peshmerga explained as an artillery barrage called in by the Kurds temporarily replaced the rattle of small arms from Peshmerga and IS firefights.

“They are firing from inside and around that building with the green roof,” said one Peshmerga officer pointing to what looked like a warehouse a few hundred yards away in the village of Dere. The building sat at the foot of the shallow hillside from where we overlooked the village from behind the limited cover of a sand bank.

No sooner had the officer spoken than a mortar round fell just short of us, kicking up a cloud of dune-coloured dust and provoking a cluster of Peshmerga to shoulder their weapons. Some edged up to the top of the bank concerned that such a close explosion might herald a more intensive attack from IS. Every now and then an ambulance would speed past, skirting our position, the crew taking enormous risks to ferry out Peshmerga casualties from frontlines close to Barima. Parked behind our bank one ambulance, its white paint work entirely smeared with ochre-coloured dirt to give it an improvised desert camouflage, sat ready to evacuate wounded.

Its crew, when not preparing their triage equipment inside the vehicle, moved around handing out bottled water to the Peshmerga, the ambulance men’s small medical bags and rolls of surgical tape dangling from their belts.

By midday Thursday, news filtered through to our position that suicide truck bombers had attacked Kurdish fighters in Fazilya, another of the villages nearby that the Peshmerga was fighting to clear of IS.

“We stopped one of the trucks with rockets but the other got close and we have several seriously wounded,” the officer overlooking Dere told me. Later reports confirmed that one Peshmerga had both legs blown off in the attack. Five other Kurdish fighters were killed that day by roadside bombs across all three frontlines. For the first time too since the start of this offensive, an American soldier, most likely one of the numerous Special Forces troops working alongside the Kurdish and Iraqi advance was also killed.

While the Peshmerga have not released any official casualty figures from Thursday’s offensive, it’s believed that perhaps as many as a dozen Peshmerga were killed and many more wounded.

Later that day we finally made our way back to what we thought was the comparative safety of the Peshmerga base at Tel Iskuf. Reunited with our driver, Bekus, he told us how shortly after our departure to join the convoy, a mortar round had passed so close overhead he had thrown himself on the ground just in time before it exploded barely yards away. Had the shell landed in the same spot earlier that morning when hundreds of Peshmerga mustered for the advance there would almost certainly would have been many more casualties, Bekus said.

And so the long-anticipated military campaign to liberate Iraq’s second largest city from IS is now full in its full terrible flow. For their part the jihadists have responded by activating sleeper cells some of which on Friday attacked the Iraqi city of Kirkuk 105 miles south-east of Mosul, killing 19 people.

Reports are emerging too of hundreds of civilians from villages like those the Peshmerga have been seeking to retake over the past week, been herded into Mosul where they are being held as human shields as the offensive draws closer to the city.

Inside Mosul itself IS’s gruesome crackdown on anyone suspected of communicating with the outside or working with resistance groups inside the city has reached new levels of barbarism.

In one of IS’s latest propaganda videos an 11-minute film called Deterring the Hirelings 2, men are forced to kneel before a jihadist approaches with a spray can. The victim’s head is then sprayed with black paint marking a target before the executioner uses a shotgun to murder him at point blank range.

Just as IS used surveillance drones last Thursday over Peshmerga positions, so too have they used them to film mass executions of alleged spies from the air as part of their latest intimidatory propaganda.

Horrendous as these acts are they will not be the last in the battle for Mosul, nor will they deter Kurdish and Iraq troops from the task at hand of liberating the city. Hard as it is to imagine let alone contemplate, the worst may yet be to come.