BAGHDAD — The biggest surprise about the raging battles that erupted last week in southern Iraq was not that the combatants were fellow Shiites, but that it took this long.
Enmity has long festered between the two sides: one a ruling party that has struggled against the widespread perception that it gained power on the back of the U.S. occupation, the other a populist movement that has positioned itself as a critic of the U.S.-backed new order.
As they vie for power before October provincial elections that will determine who controls the oil-rich south, the stakes are high not only for the Supreme Islamic Iraqi Council, the largest Shiite faction in the Iraqi coalition government, and the Mahdi Army, the militia loyal to cleric Muqtada Sadr.
The conflict also poses great difficulties for the Americans, who are widely seen as siding with the Supreme Islamic Iraqi Council and Prime Minister Nouri Maliki's Islamic Dawa Party against Sadr.
The Iraqi government's offensive in Basra has spelled the end to a seven-month cease-fire by Sadr's militia in all but name.
In an ominous sign Saturday, Sadr in a rare TV interview praised armed resistance. Separately, he urged his followers to defy Maliki's ultimatum to surrender their weapons.
Iraqi forces battling the Mahdi Army called in U.S. airstrikes Saturday in Basra, and two American soldiers were killed in a mostly Shiite area of east Baghdad.
Sadr's cease-fire, which he imposed in August after his loyalists clashed with the Supreme Islamic Iraqi Council's militia in the southern city of Karbala, was widely credited with helping calm Baghdad.
The U.S. military now risks forfeiting gains with the Sadr group, arguably the most popular Shiite political movement across Iraq. Already, U.S. officers have reported an increase in the number of attacks against them in Baghdad, where soldiers had benefited from the Mahdi Army's tacit cooperation.
"It would be disastrous if the United States ended up as supporters on a crackdown on the Sadrists for reasons mainly to do with internal Shiite politics," said Reidar Visser, editor of the southern Iraq-related website historiae.org.
"The fight in Basra shows the folly of trying to control all the Shiites of Iraq through a small minority, which appears to be the current U.S. policy."
Many Iraqis have viewed the members of the post-Saddam Hussein administrations as isolated returning exiles, backed by Iran or the U.S. The officials' credibility has been diminished by government failings since the U.S.-led invasion -- notably endemic corruption, the lack of security and abysmal public services.
In contrast, the Sadr movement's foundations are built upon the legacy of Sadr's father, who challenged Hussein's rule in sermons and was killed in 1999. Its voice, fiercely anti-U.S. and staunchly nationalist, has emerged as one of the few alternatives for Iraqis. The movement has even survived a two-year stint in the government and, like other Shiite militias, its involvement in sectarian killings.
Sadr loyalists allege that as the elections approach, their group has been deliberately targeted by the Supreme Islamic Iraqi Council through the army and police's top commanders, where the party wields influence. The Sadr camp mostly boycotted the last local elections in January 2005, and predicts that it will rout its opponents this time.
But a senior Supreme Islamic Iraqi Council leader, Sheik Jalaluddin Saghir, said the Sadr loyalists were trying to cover up their criminal activities with the allegations of politically motivated attacks.
"They have an overt plan to control the provinces; this is what is happening. They want to take over certain provinces. There is no hiding this," he said. "They will deal with the devil, they will deal with criminal elements if it helps them reach their goals."
The dislike runs deep. Sadr loyalists curse members of the rival group's armed wing, the Badr Organization, with a play on words, calling them "Ghadr" -- Arabic for treachery. Mahdi Army fighters accuse the Badr Organization of killing Sunnis in Baghdad and then blaming it on them.
In turn, asked about Sadr, one senior official from the Supreme Islamic Iraqi Council answered coldly: "You know what they say, once a problem, always a problem."
The animosity is also rooted in a historic rivalry between the Sadr family, long seen as a champion of the underclass, and the Supreme Council's senior leader, Sheik Abdelaziz Hakim, son of a conservative grand ayatollah, whose family traditionally enjoyed the support of the country's Shiite merchant class.
Observers warned a year ago that the situation in the Shiite-majority south was deteriorating as anger mounted within the Mahdi Army over delays in holding provincial elections. Then, the senior coalition commander in the southern city of Diwaniya, Polish Maj. Gen. Pawel Lamla, said that an increase in Shiite militia violence could be traced to the power struggle.