The Iraqi capital locked down by curfew. U.S. diplomats holed up their workplaces, fearing rocket attacks. Nearly every major southern city racked by turmoil. Hundreds killed in less than a week.

A declaration Sunday by Shiite cleric Muqtada al-Sadr to pull his Mahdi Army fighters off the streets may help bring an end to the wave of violence that swept Baghdad and Shiite areas after the government launched a crackdown against militias in Basra.

That will ease the violence which has claimed more than 300 lives. But it won't bring an end to the power struggle between Shiite parties that triggered the confrontation.

Nor will it ensure government control of Basra, Iraq's second-largest city and headquarters of the vital oil industry.

And it could leave Prime Minister Nouri al-Maliki politically weakened because he put his prestige on the line with promises to crush Basra's "criminal gangs," some of which he said were "worse than al-Qaida."

Instead, the bloody confrontation serves as a reality check about the situation in Iraq -- even as the top U.S. officials in Baghdad prepare to brief a skeptical Congress next week about prospects for bringing home the troops and leaving a relatively stable country behind.

U.S. President George W. Bush called the Basra crisis "a defining moment" because the Maliki-led Iraqi government was finally taking on the Shiite militias.

But the crisis speaks volumes about the reality of Iraqi society and raises new questions about the effectiveness of the country's leadership as America debates whether continuing the mission here is worth the sacrifice.

Iraqi and American officials portrayed the crackdown as a move to crush outlaw militias -- some with close ties to Iran -- that have effectively ruled the streets of the country's second-largest city for nearly three years.

Many of those armed groups are without question deep into oil smuggling, extortion, murder and robbery.

But the picture is more complex. It involves deep-seated rivalries within the majority Shiite community.

Numerous other militias and armed groups operate in Basra and elsewhere in the south -- some with close ties to political parties in the national and provincial governments.

All signs indicate that the crackdown was directed primarily at the Mahdi Army, the armed wing of al-Sadr's political movement.

The Sadrists believe the goal was to weaken their movement before provincial elections this fall. Al-Sadr's followers expect to make major gains in the regional voting at the expense of al-Maliki's Shiite partners in the government.

For months, al-Sadr and other Shiite parties have been locked in a bitter power struggle for control of the Shiite south -- which contains the bulk of the country's proven oil reserves as well as major religious shrines that attract millions of pilgrims.

Last August, al-Sadr proclaimed a unilateral cease-fire nationwide in an effort to reorganize the force and rein in factions that had branched out into crime.

U.S. commanders acknowledge that truce helped bring down violence in Baghdad.

Nonetheless, U.S. and Iraqi forces continued to chip away at the Sadrists with raids and arrests in Baghdad and elsewhere. American officials insist the target was not al-Sadr's movement but Iranian-backed renegades who did not abide by al-Sadr's cease-fire.

Al-Sadr's followers didn't see it that way.

Once the crackdown began in Basra, they rose up all over the Shiite heartland, launching rockets into the U.S.-protected Green Zone in Baghdad, firing on American patrols, burning offices of al-Maliki's political party and attacking government installations.

The fact that al-Maliki apparently miscalculated the response casts doubt on his judgment and raises serious questions about his commitment to the U.S. goal of national reconciliation.

Despite the Mahdi Army's unsavory image, a number of key U.S. commanders and officials here have long maintained that it is a mistake to demonize the entire Sadrist movement, which enjoys a substantial following among millions of Iraqi Shiites.

It would be a mistake to assume that U.S. goals and al-Maliki's goals are fully aligned, said Middle East expert Jon Alterman.

"Our (the U.S.) preference is for many voices to be reflected in whatever Iraqi government emerges from five years of conflict," Alterman said. But, "al-Maliki is playing a long-term game for all the marbles."

The Basra confrontation also served as a test for the U.S.-trained Iraqi security forces, which are majority Shiite and include many al-Sadr supporters.

In the campaign's first days, Iraqi forces made little headway against Mahdi fighters, who unleashed rocket-propelled grenades and machine gun fire every time government troops tried to enter their neighborhoods.

The headquarters of the Iraqi army's Basra operation has come under fire regularly since the fighting began. Iraqi commanders have had to turn to the British and American warplanes to take out militia fighters blocking their advance.

At least a dozen police, including some elite commandos, defected to the Sadrists in Baghdad. AP Television News video showed Mahdi fighters in Basra unloading weapons from an Iraqi army vehicle.

The vehicle didn't have a scratch on it, suggesting it was either abandoned by the Iraqi soldiers or delivered to the Mahdi Army.