Iraq crisis: Baghdad prepares for the worst as Islamist militants vow to capture the capital

Iraq is breaking up. The Kurds have taken the northern oil city of Kirkuk that they have long claimed as their capital. Sunni fundamentalist fighters vow to capture Baghdad and the Shia holy cities further south.

Government rule over the Sunni Arab heartlands of north and central Iraq is evaporating as its 900,000-strong army disintegrates. Government aircraft have fired missiles at insurgent targets in Mosul, captured by Isis on Monday, but the Iraqi army has otherwise shown no sign of launching a counter-attack.

The nine-year Shia dominance over Iraq, established after the US, Britain and other allies overthrew Saddam Hussein, may be coming to an end. The Shia may continue to hold the capital and the Shia-majority provinces further south, but they will have great difficulty in re-establishing their authority over Sunni provinces from which their army has fled.

It is unlikely that the Kurds will give up Kirkuk. “The whole of Kirkuk has fallen into the hands of peshmerga [Kurdish soldiers],” said the peshmerga spokesman Jabbar Yawar. “No Iraqi army remains in Kirkuk.”

Foreign intervention is more likely to come from Iran than the US. The Iranian President Hassan Rouhani said that Iran would act to combat “the violence and terrorism” of Isis”. Iran emerged as the most influential foreign power in Baghdad after 2003. As a fellow Shia-majority state, Iraq matters even more to Iran than Syria.

Iran will be deeply alarmed by the appearance of a fanatically Sunni proto-state hostile to all Shia in western Iraq and eastern Syria. Abu Mohamed al-Adnani, the Isis spokesman, said today that the Shia, 60 per cent of the Iraqi population, “are a disgraced people”, accusing them of being “polytheists”.

Iraq’s Shia may well conclude that their army has failed them and they must once again rely on militias like the Mehdi Army which was responsible for the slaughter of Sunni in 2005 and 2006. At that time, much of Baghdad was cleansed of Sunni. The loss of Baghdad has never been forgotten or forgiven by Sunni states such as Saudi Arabia, which has long hoped to reverse the Shia dominance in Iraq.

In Mosul, Isis has so far been careful not to alienate the local population which on the west bank of the Tigris River is Sunni. There are large Kurdish neighbourhoods in the east of the city. Refugees are finding it difficult to enter the Kurdistan Regional Government zone because of stringent checks and single men, suspected of being insurgents, are not allowed entry.

The Kurds are taking advantage of the disarray of the government in Baghdad to seize territories along the “trigger line”. This stretches from north-east of Baghdad to the Syrian frontier west of Mosul. The Iraqi Kurds have advanced further towards establishing an independent state, but it is unclear how far they will commit troops to rescue the Baghdad government.

Iranian intervention would probably come through massively strengthening Shia militias. But the Iraqi Prime Minister Nouri al-Maliki will find it very difficult to reverse the defeats of the last week.