New York Times News Service

BAGHDAD — When he heard Tuesday that Mosul, Iraq’s second largest city, had fallen to Sunni militants, Abu Ali Alakabaie knew what he had to do.

One of a number of Iraqi Shiite commanders who had been fighting on behalf of President Bashar Assad of Syria in recent years, he quickly packed his belongings and hit the road, racing to Baghdad, where he had heard that the militants were already reaching the northern suburbs.

“After they occupied Mosul, we decided to come back from Syria to back the security forces here,” he said.

He arrived in Baghdad on Tuesday, joining a growing throng of Iraqi militia commanders and fighters eager to put to work here the finely honed skills they had accumulated in years of fighting in Syria some of the same Sunni militants who were attacking Iraq. “We now have great experience in guerrilla fighting,” he said, adding diplomatically, “The Iraqi army has no experience doing that.”

As he spoke Friday evening, hundreds of young Shiite men streamed past him, massing in a basketball arena in eastern Baghdad, lining up before recruiters like college students at a job fair. The officials took their names and addresses, to run background checks before adding them to the militia ranks.

It wasn’t just one Shiite militia group recruiting but at least four — and perhaps more. It was hard to tell in the confusion as Shiites responded by the thousands to the call to arms issued earlier in the day by Grand Ayatollah Ali al-Sistani, to protect fellow Shiites and to prop up the Shiite government of Prime Minister Nouri al-Maliki.

It was only three weeks ago that Maliki was elected for a third term, by a surprisingly strong margin. Yet, his country now seemed in danger of slipping away from him. Sunni militants were in control of Mosul and Tikrit, Saddam Hussein’s hometown, while the Kurds, ostensibly his allies, had taken over Kirkuk, Iraq’s oil-rich city, which they had long coveted.

But it was more than that, as Iraq’s millions of Shiites knew very well. The U.S. invasion and occupation had handed them a once in a millennium opportunity to rule over Iraq. And now, in a matter of five or six years, they seemed on the verge of squandering it. The sacred Shiite shrines at Samarra, Karbala and Najaf were threatened by the militants and their leaders in the Islamic State of Iraq and the Levant, who had sworn to level the sites.

But the idea of bringing back Shiite militias sent a shudder through many, raising chilling memories of the sectarian war that raged in Iraq from 2005 through 2008, with torture chambers, ethnic cleansing of neighborhoods and bodies dumped in the Tigris with holes drilled in victims’ heads. Such a war, once unleashed, would be hard to quell, and Shiite leaders were well aware that the Sunni militants were willing to start one.