These are tense days in Baghdad, full of anticipation and fear, marked with the faces of men drawing burial wraps around their heads in preparation for an unspecified death. The sense of conflict is pervasive and entrenched, and it is coupled with widespread feelings of bitterness and frustration at the Iraqi government’s inability to establish security. Aided by a daylong curfew that helped keep the streets clear during the march, today’s rally in the impoverished Baghdad neighborhood was largely peaceful, interrupted only by a single rocket attack that went astray and caused no casualties. But elsewhere in Iraq, 23 more people died, mostly policemen gunned down by insurgents. In the northern city of Mosul, a suicide bomber drove into the middle of a soccer match, killing 10 in the second attack on a sporting event in as many days. Iraqi officials have by and large ceased claiming that security is under anyone’s control. Instead, as today’s march seemed to indicate, security is deteriorating in step with the ramping up of just the kind of militia activity that is plunging Iraq into civil war . As marchers in Sadr City prepared to raise their fists, U.S commanders in Washington bowed their heads before Congress and began to face this reality. “I believe sectarian violence is probably as bad as I’ve ever seen it, in Baghdad in particular,” said Gen. John Abizaid, the senior U.S commander for the Middle East, in testimony to the U.S Senate Armed Services Committee yesterday, “If not stopped, it is possible that Iraq could move toward civil war.”

Signs of this slide are already evident here in Baghdad, where many Iraqis are reluctantly starting to accept that militias may be better than the government at providing security. Militia leaders are playing upon this exasperation with the government. Armed groups representing ethnic sects, ministerial blocs and political alliances are openly flouting the government’s calls for unity, and are encouraging the delegation of security responsibilities to smaller groups. “We cannot face terror without the support of the people,” Hadi al-Amiri, secretary-general of the Badr organization—previously known as the Badr Brigades—told NEWSWEEK. The Badr organization has officially agreed to cede its weapons to the Iraqi government, but concerns persist among U.S. officials and ordinary Iraqis that some members of the group may be involved in death squads and kidnappings. “I think that all the people of every neighborhood should handle the protection of their district. The Sunni areas should have Sunnis to protect them. The same goes for Shiite areas.”

That sentiment is being echoed in other powerful quarters as well. Abdul Aziz al-Hakim, leader of the powerful Supreme Council for Islamic Revolution in Iraq, this week called for neighborhoods to organize themselves into popular-defense committees. In Najaf, hundreds of supporters of this concept gathered in formation lines in yet another show of force, and a rebuttal of the government’s efforts to disband militias. Since his government took office in March, Prime Minister Nuri al-Maliki has been trying to develop a security plan for Baghdad, the site of the worst sectarian violence in the country and the most likely flash point for future confrontations between militias and the government. The initial implementation of Maliki’s plan failed and led to last week’s announcement by the Bush administration that several thousand more U.S troops would be diverted from other parts of the country to help out in Baghdad. Maliki contended that the first part of his security plan was simply identifying the source of the security problem—the militias. Now, he says, the plan is to move against them.

But the militias may move back. Emboldened by the ferocity of Hizbullah’s resistance in Lebanon, and the sense of entitlement that has grown up around the political rise of their leader, Moqtada al-Sadr, the Mahdi Army has become one of the thorniest challenges for the Iraqi government. “The biggest problem in Baghdad now isn’t Al Qaeda anymore,” says one U.S military intelligence analyst, “It’s the Mahdi Army, make no mistake about it.” The timing of today’s march couldn’t have been more cleverly calculated. The thousands of marchers came from all over Iraq. Heeding al-Sadr’s call for a “Million-Man March,” they began arriving in the capital Thursday night from Basra, Nasiriya, Kut and elsewhere. “We all volunteered to come,” said one marcher, “and we are all ready to fight.” The march was one of the single biggest shows of support for Hizbullah anywhere in the world since the conflict began more than three weeks ago. Demonstrators burned U.S and Israeli flags and scuffed their shoes on the pictures that had been drawn in the street.

For all his bluster, however, there are signs that al-Sadr may be facing a rebellion of his own. U.S military and Western analysts believe that the Mahdi Army is deeply divided, with lower-level commanders vying for control and influence in an organization that has tripled in size since its inception in 2003. Key Mahdi Army leaders have openly disagreed with al-Sadr’s increased cooperation with the government—some of his key officials are in the cabinet—and are thought to be pursuing their own, often violent and sectarian, aims. Some Iraqis, however, dispute any suggestions that the Mahdi Army is behind any violence. “Moqtada has full control over the Mahdi Army,” says Hadi al-Amiri, the head of Badr. “These terrorist acts are carried out by people who claim to be Mahdi Army members.” Either way, the news isn’t good for Maliki and his struggling government. Faced with an organized group, Maliki will have to move quickly and forcefully against armed men buoyed by the fervor of resistance and rebellion in Bint Jbail, Tyre and other towns of southern Lebanon. If there are splits, he faces not just one ideology, but many. He doesn’t have much time. And Iraqis don’t have much patience.