Before Britain gets involved in another intervention against Sunni insurgents in Iraq, David Cameron should read the Koran. Verse 216, Chapter 2 says: "You may hate a thing which is good for you, and you may love a thing which is bad for you. God knows, while you do not know."

Wise words for a British prime minister tempted to delete all those humiliating memories of Basra. The two knee-jerk responses to the sudden and complete collapse of Western "post-war" policy in Iraq, are: arming the Kurds and placing all chips on the new man, Haider al-Abadi.

Everyone loves him, but will he prove to be good for his lovers? Some, maybe, but not all. Syrian historian Sami Moubayed is far from convinced. He wrote in the Middle East Eye: "Abadi is not a moderate -- far from it -- and nor is he less Islamic driven than Nuri al-Malki... Shiite Islam is the crux of his ideology. And he couldn't possibly have been named premier without the blessing of the Iranian government."

Abadi's backers should now be asking themselves uncomfortable questions, such as why the Islamic State has got as far as it has and why it may now be difficult to dislodge. Cameron is assuming a short air campaign, but why should it be as short lived as Nato's in Libya? Think instead of the parallel that Taliban in Afghanistan offer, where no matter how desperate the Pashtun become about the insurgency, they are more frightened of the corrupt tyranny of the ruler of Kabul. Better to have an honest tyrant rather than a corrupt one.

Armament, organization and ideology are all part of IS's rise. But the most important part of their arsenal has little to do with military prowess or religious fervor, although both help. It is their promise to carve a Sunni majority state out of the wreckage of two broken Shia dominated ones -- Syria and Iraq.

Post-Saddam Iraq is a sectarian construct in which power is allotted by ethno-sectarian weight. Sectarianism was the formula which Iraq's first US pro-consul Paul Bremmer used for the composition of Iraq's first transitional governments -- which included 13 Shias, five Sunnis, five Kurds one Turkmen and an Assyrian. Washington likes to portray itself as suffering from attention deficit disorder in the lands it has invaded.

But the US is not an inattentive parent. It indeed took the bombing in February 2006 of the Askariya mosque in Samarra, a sacred Shia shrine, to spark the civil war, but US special forces used Shia paramilitaries for their own ends, to deflect attacks from Sunni insurgents on their troops.

Sectarianism, too, was the hallmark of Maliki's one-man rule. US funding of Sunni tribes against Al Qaida, its half hearted attempt get Maliki to absorb the Awakening into the Iraqi Army, or even their attempts today to re-awaken the Awakening, are exceptions to the rule, and come as afterthoughts. The motive for the troop surge and for buying up the Sunni tribes was to pave the way for an exit of US combat troops. It was never intended as a sustained attempt to alter the post-Saddam balance of power.

The Sunni tribes who turned against Al Qaida have been betrayed and ignored. If you are promised political power, when you lay down your arms, you have a right to expect it or you will pick those arms up again. The political experiment ended for them when the non-sectarian Iraqiya Bloc was trashed. Maliki waged a full scale war on the very people he needed.

A former insider like Ali Khedery provides a bleak assessment of how rotten rule from Baghdad had become. Khedery, the longest serving US official in Iraq from 2003 to 2009, supported Maliki, but became convinced by 2010 that the US was making a mistake of historic proportions by continuing to back him.

"Maliki's one-man, one-Dawa-party Iraq looks a lot like Hussein's one-man, one-Baath Party Iraq....There is not much "democracy" left if one man and one party with close links to Iran control the judiciary, police, army, intelligence services, oil revenue, treasury and the central bank. Under these circumstances, renewed ethno-sectarian civil war in Iraq was not a possibility. It was a certainty."

For a full year, the Sunni protest in Anbar was peaceful, but Washington did not want to know. The consensus which had been formed in that benighted capital would not be broken until the headlines "Who Lost Iraq?" once again slapped them in the face.

It is little coincidence that IS flourishes in two sectarian states where Sunnis have been marginalized, or that in declaring a new cross border state, the IS has recreated an entity with a Sunni majority -- which indeed used to dominate Iraq.

The two tasks that Abadi faces are both formidable ones. The first is to form a genuinely non-sectarian government and governance. This means genuine power sharing -- in the key ministries. The second is to face down all extremist militias, both IS and the Iranian-backed shia militias -- Asa'ib Ahl al-Haq for one. After 11 years of what must now be regarded as continuous war and political turmoil, these are enormous tasks.

Nor could any potential Iraqi premier, least of all one of Abadi's pedigree, turn his back on his sponsor Iran. Indeed Abadi has already suggested that if the US did not intervene, Iran should. Abadi owes Iran for its decision to jettison Maliki. This may have been nothing more than realpolitik. Qassem Suleimani, commander of the Quds Force of the Iranian Revolutionary Guard Corps, must have realized that Iran can not fight two wars at once.In Syria, the need to keep the Bekaa Valley open as Iran's umbilical cord to Hezbollah, trumped all other considerations for Tehran. The irony is that had they done the same with Bashar al Assad and appointed a deputy in his place, Syria might now be a different place.

Iran's deadliest enemy, Saudi Arabia, is panicking too. If the spark of revolution, which the Saudis have tried hard to stamp out, can leapfrog national borders (as it did from Tunisia, to Egypt, Yemen and Bahrain, and Syria) so, too, can the religious fanaticism of the Islamic State.

The combination of militancy and religious fervor is surely not a new one for the Arabian peninsula. They should only recall how Muhammad ibn Abd al-Wahhab made his pact with Ibn Saud the ruler of Najd, and how Wahhabism has been integral to the Saudi kingdom ever since. What happens to Sunnis in Iraq, could also happen to Sunnis in Saudi. The Saudis supported Abadi as a panic measure, but Abadi will not insure the kingdom against the same forces emerging at home.

Another US and British intervention in Iraq may halt the IS advance, but it will not address the major task of dealing with the Sunni political grievance. However monstrous the Islamic State has become, it is a monster Western intervention has created.