The gaudy mosque Saddam Hussein built to celebrate the "victory" of surviving the first Gulf War is back in the headlines today, once again for all the wrong reasons.

Yesterday, as worshipers gathered for evening prayer at Umm al-Qura mosque in Baghdad, a suicide bomber murdered 28 people. Among them was Khaled al-Fahdawi, a Sunni Arab MP from the Ramadi area in Anbar Province who had been a leading voice against Al Qaeda-aligned insurgents from his own community. The attack came as Ahmed Abdulghafur al-Samarrai was leading prayers. Mr. Sammarai is a Sunni preacher from Baghdad's Adhamiyah neighborhood, once a bastion for Sunni jihadis. He was among the clerics and tribal leaders who turned against the insurgency in the so-called Sunni "awakening" a few years ago, and is a hated figure among the hardcore.

Reuters reports that the Islamic Party of Iraq says the attack was carried out by the Islamic State of Iraq, a self-proclaimed Al Qaeda affiliate, and that the target was Mr. Fahdawi. He was the seventh member of the Sunni-based party to be murdered in the past month.

"Al Qaeda has been distributing a lot of leaflets which say that there is no repentance for IIP members anymore, and killing them is allowed everywhere," party leader Rasheed al-Azawi told Reuters.

The attack is a reminder that as US troop levels continue to dwindle (the US mandate expires at the end of this year), Iraq remains an inordinately violent place. Events at the mosque since the 2003 help illustrate the challenges Iraq continues to confront.

After the attack, Samarrai blamed Al Qaeda for the deaths, but also called for religious tolerance. "Do not describe [the attackers] as Shiite or Sunni or Iraqis," AFP quoted him as saying at the mosque during funeral services for many of the dead today. "They are terrorists and terrorists have no religion."

Perhaps. But the attack highlights the fact that there are still many in the country willing to kill and die in service of the Sunni takfiri ideology of Al Qaeda. The practice of takfir, declaring opponents to be infidels and apostates and therefore fair game for murder, is embraced by the group's fellow travelers in Iraq and elsewhere. To them, Iraq's Shiites are marked for death simply because of their beliefs, as are fellow Sunnis who reject their vision.

That's one reason that the vast majority of Iraq's Sunni Arabs are opposed to the jihadis. Thousands of Sunni Arabs have been killed at their hands for the crime of participating in Iraq's political process or rejecting violence. But the strains of sectarian division remain – with many of the country's Sunni Arabs suspicious of the Shiite-dominated government of Nouri al-Maliki and afraid of the Shiite militias, like those loyal to Moqtada al-Sadr that ran death squads at the height of the sectarian civil war a few years ago.

Some of the biggest failures, and a few of the successes, of post-Saddam Iraq run through the mosque. The mosque was built – with four minarets designed to look like scud missiles – for $10 million in the 1990s, a time when international sanctions were driving millions of Iraqis into poverty. Dubbed the "Mother of all Battles" by Hussein (his phrase for his invasion of Kuwait and crushing defeat there at the hands of a US-led coalition), it was a perfect illustration of his vainglorious excess and disregard for the public welfare. It houses a Quran he claimed was written in his own blood.

After the US invasion in 2003, the mosque was renamed "Umm al-Qura," or "Mother of all Villages" after a name for Mecca. In January 2004, I attended a meeting of both Sunni and Shiite clerics there designed to cool bubbling sectarian tensions. There were stock appeals to the unity of the community of Islam, the ummah, and ringing rejections of sectarian strife. The most popular rallying point at that meeting, however, was rejection of the United States as an occupier, which prefigured the two-front war the US would soon be drawn into against Shiite and Sunni fighters, who hated the US as much as they hated each other.

At that meeting, I caught my first glimpse of Harith al-Dhari, a Sunni preacher about to take on a glaringly important role. "Some may think that our history stopped when we were occupied by this great power," he said then. "But we fought the British, and now will fight the occupiers. The only power that's undefeatable is God. Now we must liberate Iraq."

I was told Mr. Dhari commanded respect as both an Islamic scholar and as the grandson of a man said to have murdered a British Army officer in 1920, sparking an Iraqi uprising. Dhari had returned home from exile in the United Arab Emirates in 2003, and quickly started building a political base for his extremist views. He took over the mosque (he was the one who renamed it) and founded the Association of Muslim Scholars, a Sunni group that had deep ties to the Sunni insurgency. The rhetoric of Islamic unity was soon abandoned.

During the kidnapping spree in the coming years, members of his association became the first port of call for those seeking the release of friends and relatives, and he was often able to deliver results. In 2004 alone, Dhari was able to negotiate the release of at least a dozen hostages. Over time, the mosque and the Adel neighborhood that surrounded it developed a dark reputation. I used to visit semi-regularly to talk politics and religion. One day in the summer of 2005, I emerged from a cordial tea-fueled meeting to find the Monitor's long-term driver ashen-faced. As we pulled away he turned to me and said: "The guards told me I deserve death for working with the infidels." We never went back.

In the coming years, the neighborhood around the mosque devolved into a free-fire zone, with kidnappings and sectarian killings by both Shiite and Sunni militias. Monitor translator Alan Enwiyah was murdered in the area during the abduction of former Monitor reporter Jill Carroll.

In 2007, US forces raided the mosque, making over a dozen arrests. The Association of Muslim Scholars was kicked out. Mr. Samarrai, a founding member of the group who split with it over what he deemed the intolerance of many of its members, was then named the head of the Sunni Endowment, or waqf, a national, semi-official body headquartered at Umm al-Qura that holds mosques and other religious property in trust.

In recent years the mosque has been, well, a mosque again, and Samarrai has been an important voice calling for Iraq's sectarian divisions to be healed.

But the murders there yesterday are a reminder that Iraq's battle for the future continues.

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