It seems to be an iron law of Iraqi politics, as immutable as the rising and setting of the sun: when Sunni militants run wild, Shiite militants retaliate in kind. For the past year we have been hearing a great deal about the return of al-Qaeda in Iraq, which has now been transformed into the Islamic State of Iraq and Syria. In that guise, the group has been expanding its control on both sides of the Syria-Iraq border, its most alarming gains being the seizure of Fallujah. Al-Qaeda terrorists have also been setting off numerous car bombs in Baghdad and other cities, killing a growing number of civilians, many of them Shiites. Indeed January saw the highest death toll since April 2008.

So it should be no surprise that Shiite extremists are beginning to retaliate in kind. The Mahdist Army, run by Moqtada al Sadr, is largely defunct but out of its remains have sprung fresh, Iranian-supported groups such as Asaib Ahl al-Haq and Kataib Hezbollah. Meanwhile the Badr Organization, Sadr’s old rival, remains very much in business as well, and many of its members are enlisted in the security forces where they are well positioned to use their uniforms as cover for ethnic cleansing–something last seen on a large scale in 2007.

The Washington Post quotes one Asaid Ahl al-Haq commander as saying, “We have to be much more active. Those who are trying to incite sectarianism, we have to deal with them,” while “drawing his hand over his throat like a knife.”

This is yet another ominous sign of how Iraq is sliding back toward the abyss from which it was only narrowly rescued in 2007-2008 by the U.S.-led surge. The crux of General David Petraeus’s strategy was to target al-Qaeda first in the expectation that, once its threat had receded, Shiites would turn away from militant groups claiming to defend them. This gamble paid off in 2008 when Prime Minister Maliki targeted Sadrists in both Basra and Sadr City. Such a strategy could work again, but Maliki first would have to do a better job of recruiting Sunni sheikhs to his side to turn the tide against al-Qaeda and then he would have to show willingness to turn once again on his Shiite brethren.

In short, the onus is once again on the prime minister to show statesmanship and vision–neither, alas, one of his strong suits to judge by his record in office.