*Abu Anis only realised something unusual was happening when he heard the sound of explosions coming from the old city on the western bank of the Tigris as it runs through Mosul. *

“I phoned some friends over there, and they said armed groups had taken over, some of them foreign, some Iraqis,” the computer technician said. “The gunmen told them, ’We’ve come to get rid of the Iraqi army, and to help you.’”

The following day, the attackers crossed the river and took the other half of the city. The Iraqi army and police, who vastly outnumbered their assailants, broke and fled, officers first, many of the soldiers stripping off their uniforms as they joined a flood of panicked civilians.

It was 10 June 2014, and Iraq’s second biggest city, with a population of around two million, had just fallen to the militants of the group then calling itself Islamic State in Iraq and al-Sham/the Levant (Isis or Isil).

Four days earlier, black banners streaming, a few hundred of the Sunni militants had crossed the desert border in a cavalcade from their bases in eastern Syria and met little resistance as they moved towards their biggest prize.

Rich dividends were immediate. The Iraqi army, rebuilt, trained and equipped by the Americans since the US-led invasion of 2003, abandoned large quantities of armoured vehicles and advanced weaponry, eagerly seized by the militants. They also reportedly grabbed something like $500m from the Central Bank’s Mosul branch.

“At the beginning, they behaved well,” said Abu Anis. “They took down all the barricades the army had put up between quarters. People liked that. On their checkpoints they were friendly and helpful – ‘Anything you need, we’re here for you.’”

The Mosul honeymoon was to last a few weeks. But just down the road, terrible things were already happening.

As the Iraqi army collapsed throughout the north, the militants moved swiftly down the Tigris river valley. Towns and villages fell like skittles. Within a day they had captured the town of Baiji and its huge oil refinery, and moved on swiftly to seize Saddam Hussein’s old hometown, Tikrit, a Sunni hotbed.

Just outside Tikrit is a big military base, taken over by the Americans in 2003 and renamed Camp Speicher after the first US casualty in the 1991 “Desert Storm” Gulf war against Iraq, a pilot called Scott Speicher, shot down over al-Anbar province in the west.