Volunteer Shiite fighters, who support the government’s battle against the Islamic State, peer over the rubble in Fadhiliyah, Iraq on February 24, 2015.AHMAD AL-RUBAYE/AFP / Getty Images
Iranian-backed Shia militias have succeeded recently in pushing back Islamic State's pop-up caliphate in parts of Iraq and Syria, but the very success of the Shia operation is of growing concern to the United States, some of its Arab allies and Israel, who fear the creation of an Iranian-backed "Shia Crescent" stretching from Iran to Lebanon.
While U.S. efforts to rebuild and train Iraq's army are moving at a glacial pace, Shia militia groups such as the powerful Badr Organization have been quick off the mark. Last summer, when Islamic State first swept across central Iraq, it was Badr and other Shia forces that safeguarded Baghdad. Most recently, these groups drove IS forces from Diyala province, north and east of the capital.
While many Iraqis are applauding the success of the Shia militias, it is Iran that is gaining influence as the militia campaign liberates extensive parts of Sunni Iraq, often driving out Sunni residents in the process.
Under Iranian leadership and using Iranian-supplied weapons, the force, that numbers tens of thousands, has moved to help secure oil-rich Kirkuk province, much to the concern of Kurdish leaders who claim the area for their people and have been holding the line against IS advances until now.
The emotional reaction to some of the barbaric IS executions may steel the resolve of those taking the fight to IS forces, but it also plays right into the hands of the Shia militias. As Hassan Nasrallah, leader of Lebanon's Shia Hezbollah movement, declared earlier this month, Islamic State is the greatest threat to the region and called on all Arab states to join him in fighting it.
Washington would be the last to ally itself with such Shia forces as Hezbollah or Badr. Nevertheless, the U.S.-led coalition against Islamic State, which includes Canada, has been bombing IS strongholds, thereby making things easier for the Shia campaign too.
As it conquers districts occupied by IS forces, the Badr Organization, in particular, has summarily executed Sunni residents believed to have collaborated with Islamic State and demolished homes of people who fled.
"Residents have nowhere to turn for protection," said Joe Stork, deputy Middle East and North Africa director of Human Rights Watch, whose jihad researchers documented scores of cases of ethnic cleansing in Diyala province since Jan. 1.
This should have come as no surprise. In December, Hadi al-Amiri, the Badr Brigades commander and a former minister of transport, warned Diyala residents: "The day of judgment is coming" and "we will attack the area until nothing is left. Is my message clear?"
Recently, a prominent Sunni sheik, Qassem Swedan, his son and their bodyguards were gunned down in Baghdad, reportedly by Shia militiamen.
In places such as Anbar province, mostly overrun by IS forces, the Sunni residents are torn between wanting help to get rid of Islamic State and wanting help from Islamic State to keep out the Shia militias.
This parallel struggle against Shia militias "will probably prove far more consequential than the war against the self-styled Islamic State," warned Michael Knights, an Iraq and Iran specialist at the Washington Institute for Near East Policy.
"The current conflict has boosted the profile and influence of Iranian-backed Shia militias to previously unforeseen levels," he wrote in a new study entitled The Long Haul. Mr. Knights noted that Iraq's Minister of the Interior, Mohammed al-Ghabban, is once again a member of the Badr Organization, as was the case when Iraq's violent sectarian battles were at their worst.
"If the United States loses Iraq in the process of defeating [Islamic State], it will have achieved a Pyrrhic victory on a monumental scale," cautions Mr. Knights.
In that event, some of the Iraqi militias likely would be deployed to Syria to guarantee the survival of the Assad regime, he predicted. And "the much-narrated fear of a Shia Crescent stretching from Iran to the Mediterranean coasts of Syria and Lebanon would become a real prospect."
The idea of an Iranian-dominated bloc of states right on their borders is Saudi Arabia and Israel's worst nightmare.
In Syria, Shia militias led by Hezbollah already are having some success in driving Islamic State fighters from Aleppo and in keeping the jihadists out of the south.
The only way to prevent this Shia Crescent from becoming a reality is by countering Iran's influence in Iraq. And the only way to do that, Mr. Knights said, is for the United States to commit itself to a long-term engagement in Iraq – a decade or more, he says – to ensure the Iraqi security forces win the battle against Islamic State.
The administration of U.S. President Barack Obama was reasonably quick in creating the Western and Arab coalition against Islamic State and in launching the aerial attacks on IS targets both in Iraq and Syria, but it has been slow in helping Iraq re-establish the state's
own fighting force.
Iraqi and Kurdish officials predict it will take at least until the fall before an assault on Islamic State's occupation of Mosul, the centre of its empire, will begin. The Kurds have little to gain from liberating Arab Mosul and it will take several more months before Iraqi security forces have the ability to maintain and supply a large enough force that far from Baghdad.
To achieve all this, and determined not to have too many U.S. boots on the ground doing the fighting, the Obama administration has endorsed the idea put forward by Iraq's Sunnis that it should be local people who retake local communities.
This notion hinges on a plan to create "national guard" units in each province, comprised of locals, funded by the federal government. The idea is supported by Iraq's new more-inclusive Shia Prime Minister Haider al-Abadi, but it has yet to gain parliamentary approval. Certain Shia and Kurdish MPs are apparently blocking its passage.