If they cannot, then the question becomes whether Iraq can survive as an integral country.

Maliki, a Shiite Muslim politician, has asked parliament to declare a state of emergency following the debacle in mostly Sunni Ninevah province, even as he tries to ease his way into a third term after winning a plurality of votes in parliamentary elections last month.

In Mosul, which has a population of nearly 1.8 million, ISIL faced no resistance.

"We, and every other concerned authority, knew they were coming, and which side of the city they would take first," Esmat Rajab, head of the Kurdistan Democratic Party office in Mosul, said on Wednesday.

He was referring to the part of Mosul that housed the provincial council, ministerial buildings as well as the military headquarters.

"We thought the Iraqi army and local police would remain on duty at the five bridges which connect the city, and that they would basically fight ISIL from those positions, on the other side of the city. But we were wrong." Rajab, who fled to the autonomous province of Kurdistan, where his KDP is one of the major political parties, put the blame on the composition of the army, which he said was "based on sectarian allegiances", had no loyalty to the region, and saw no point in defending it.

He estimated there were no more than 1,000 armed ISIL fighters, supplemented by other disaffected local forces.

"If the army had resisted them, there is no way they would have been able to capture the whole city. It's a big place, and even with 10,000 fighters, it would be tricky," he said. Local journalists said there were at least 20,000 soldiers and police officers available to defend the town.

The composition of the army is not the only reason the central government isn't likely to recapture Mosul quickly. A second reason is the deep distrust Sunnis and Kurds hold for Maliki, who seemingly prefers to keep the pot boiling to secure his own constituency rather than resolve the country's economic, territorial and other disputes.

A third reason to doubt a rapid restoration of central government power is Maliki's record in Fallujah and parts of Ramadi, major Sunni cities that have become ISIL strongholds since the beginning of this year. Critics say Maliki's efforts to reconquer the cities have been completely counter-productive. Where a counter-insurgency strategy is called for, which would seek to win the "hearts and minds" of the local population and gain their input into intelligence-gathering, Maliki instead has relied on heavy weapons, including barrel-bombs, the deadly unguided munitions that have been blamed for hundreds of civilian deaths in Syria.

Their use in Fallujah has alienated the civilian population.

"That's what they always do in Fallujah and in Anbar province. Only if the Iraqi army reorganised itself could it win back Mosul - and after months of fighting," Assad said.

Timeline of Iraqi jihadists' warpath since US withdrawal from country

Two-and-a-half years after the US withdrawal from Iraq, jihadists now control swathes of the country's northwest along the border with Syria, where they are also fighting.

Below are the main developments in the jihadists' advance, which has been facilitated by the internal conflict between the Sunni minority and the ruling Shiites:

On December 22, four days after the US withdrawal from Iraq, a series of attacks in Baghdad, in which 60 are killed, is claimed by a branch of al Qaeda, the Islamic State of Iraq (ISI). Led by the shadowy Abu Bakr al-Baghdadi, ISI was set up after the US-led invasion in 2003. The ISI is particularly influential in the provinces of Anbar, Nineveh and Kirkuk, where a jihadist insurrection inflicted heavy losses on US forces between 2003 and 2006, especially in Fallujah in Anbar province.

Considering itself mistreated and sidelined from positions of power, Iraq's Sunni minority launches massive demonstrations, which continue throughout last year, especially in Anbar.

Fuelled by Sunni ire and the conflict in Syria, unrest reaches its worst point in five years, with 9,475 civilians killed in 2013 according to the non-governmental organisation Iraq Body Count.

On a daily basis, bombs devastate markets, mosques and even funerals. The jihadists attack prisons and army barracks.

Security forces try to react by breaking up Sunni camps and carrying out huge operations against the jihadists.

Allied to some Sunni tribes and benefiting from the sprawling desert in the west to hide out, jihadists claiming allegiance to the Islamic State of Iraq and the Levant (ISIL), an offshoot of the ISI and which also operates in Syria, emerge in April.

On January 2-4, jihadists take control of Fallujah and parts of Ramadi, and Baghdad faces losing control of major towns for the first time since the US invasion in 2003. Up to 500,000 people may have fled the fighting, according to the United Nations.

On May 5, insurgents attack Samarra, 110km to the north of Baghdad, a symbolic city since an attack against a revered Shiite shrine in 2006 sparked the sectarian war of 2006-2007. After fierce fighting, the army, helped by tribal members, retakes the city.

A month later jihadists attack the university of Anbar in Ramadi and targets in Mosul, the country's second biggest city. On Tuesday, ISIL and other jihadists seize Mosul and take control of Nineveh province, sparking a mass exodus. They also overrun sections of the nearby provinces of Kirkuk and Salaheddin.

The authorities seem powerless faced with the jihadists' dazzling advance. Prime Minister Nouri al-Maliki offers to arm civilians to take on the insurgents.