WASHINGTON - President Bush and his aides, explaining their reasons for sending more American troops to Iraq, are offering an incomplete, oversimplified and possibly untrue version of events there that raises new questions about the accuracy of the administration's statements about Iraq.

President Bush unveiled the new version on Wednesday during his nationally televised speech announcing his new Iraq policy.

"When I addressed you just over a year ago, nearly 12 million Iraqis had cast their ballots for a unified and democratic nation," he said. "We thought that these elections would bring Iraqis together - and that as we trained Iraqi security forces, we could accomplish our mission with fewer American troops.

"But in 2006, the opposite happened. The violence in Iraq - particularly in Baghdad - overwhelmed the political gains Iraqis had made. Al-Qaida terrorists and Sunni insurgents recognized the mortal danger that Iraq's election posed for their cause. And they responded with outrageous acts of murder aimed at innocent Iraqis.

"They blew up one of the holiest shrines in Shia Islam - the Golden Mosque of Samarra - in a calculated effort to provoke Iraq's Shia population to retaliate," Bush said. "Their strategy worked. Radical Shia elements, some supported by Iran, formed death squads. And the result was a vicious cycle of sectarian violence that continues today."

That version of events helps to justify Bush's "new way forward" in Iraq, in which U.S. forces will largely target Sunni insurgents and leave it to Iraq's U.S.-backed Shiite government to - perhaps - disarm its allies in Shiite militias and death squads.

But the president's account understates by at least 15 months when Shiite death squads began targeting Sunni politicians and clerics. It also ignores the role that Iranian-backed Shiite groups had in death squad activities prior to the Samarra bombing.

Blaming the start of sectarian violence in Iraq on the Golden Dome bombing risks policy errors because it underestimates the depth of sectarian hatred in Iraq and overlooks the conflict's root causes. The Bush account also fails to acknowledge that Iranian-backed Iraqi Shiite groups stoked the conflict.

President Bush met at the White House in November with the head of one of those groups: Abdul Aziz al-Hakim of the Supreme Council for the Islamic Revolution in Iraq. SCIRI's Badr Organization militia is widely reported to have infiltrated Iraq's security forces and to be involved in death squad activities.

Secretary of State Condoleezza Rice recited Bush's history of events on Thursday in fending off angry questioning from Sen. Barbara Boxer, D-Calif., about why Rice had offered optimistic testimony about Iraq during a Senate Foreign Relations Committee hearing in October 2005.

"The president has talked repeatedly now about the changed circumstances that we faced after the Samarra bombing of February `06, because that bombing did in fact change the character of the conflict in Iraq," Rice said. "Before that, we were fighting al-Qaida; before that, we were fighting some insurgents, some Saddamists."

She cited the version again in an appearance later that day before the House Foreign Affairs Committee. "This is a direct result of al-Qaida activity," she said, asking House members not to consider Iraq's sectarian violence as evidence that Iraqis cannot live together.

Bush's national security adviser Stephen Hadley used the same version of events in an appearance Sunday on NBC's "Meet the Press."

Much like the administration's pre-war claims about Saddam's alleged ties to al-Qaida and purported nuclear weapons program, the claims about the bombing of the Shiite mosque in Samarra ignore inconvenient facts and highlight questionable but politically useful assumptions.

No one disagrees that the February bombing of the Golden Dome shrine was a pivotal moment. In the days following the attack, armed Shiites stormed Sunni mosques and neighborhoods, killing hundreds. Baghdad's Sunni residents responded by arming themselves, and Sunni insurgents set off car bombs in Shiite neighborhoods. By October, the monthly death toll was reaching into the thousands.

U.S. diplomats, reporters and military and intelligence officers began reporting that Shiite death squads were targeting Sunni clerics and former officials of Saddam Hussein's Sunni regime at least 15 months before the Samarra bombing.

Then-Secretary of State Colin Powell urged a U.S. offensive against radical Shiite cleric Moqtada al-Sadr's Mahdi Army militia in 2004. But he was overruled by then-national security adviser Condoleezza Rice, then-defense secretary Donald H. Rumsfeld and Vice President Dick Cheney. They argued against fighting a two-front war against Sunni insurgents and Shiite militants.

The concerns about Shiite militias grew after the Jan. 30, 2005, elections that brought the Shiite-led government of then-Prime Minister Ibrahim al-Jaafari to power. Journalists in Iraq, the CIA station, the U.S. Embassy and the U.S. military all reported throughout 2005 that evidence was mounting that Jaafari's government was incorporating Shiite militias and death squads into the Iraqi army and police.

A year before the Samarra bombing, Hannah Allam, writing for what was then Knight Ridder Newspapers, reported that Iraq could be headed toward civil war. Knight Ridder was purchased by The McClatchy Co. last June.

"Shiite Muslim assassins are killing former members of Saddam Hussein's mostly Sunni Muslim regime with impunity in a wave of violence that, combined with the ongoing Sunni insurgency, threatens to escalate into civil war," Allam, then the news organization's Baghdad bureau chief, wrote on Feb. 27, 2005. "The war between Shiite vigilantes and former Baath Party members is seldom investigated and largely overshadowed by the insurgency."

She added, "Iraq's new Shiite leaders have little interest in prosecuting those who kill their former oppressors or their enemies in the insurgency."

The story quoted the then-spokesman for the Iraqi Interior Ministry, Sabah Kadhim: "It's the beginning, and we could go down the slippery slope very quickly. ... Both sides are sharpening their knives."

By the summer, the tortured bodies of kidnapped Sunni clerics had begun turning up regularly on Baghdad's streets, and on Aug. 10, 2005, Knight Ridder correspondent Tom Lasseter wrote:

"A militant Shiite Muslim group with close ties to Iran has gained enormous power since Iraq's January elections and now is accused of conducting a terror campaign against Iraq's Sunni Muslim minority that includes kidnappings, threats and murders."

Lasseter identified the group as the Badr Organization and reported that Iraq's interior minister was associated with it.

On Nov. 15, 2005, U.S. troops raided an Interior Ministry building in Baghdad and found 169 malnourished prisoners, many of whom had been tortured. The vast majority of the victims, if not all of them, were Sunnis.

By December, Badr's involvement in death squads was widely known.

"The Iranian-backed militia the Badr Organization has taken over many of the Iraqi Interior Ministry's intelligence activities and infiltrated its elite commando units," Lasseter wrote, on Dec. 12, 2005, citing U.S. and Iraqi officials.

"That's enabled the Shiite Muslim militia to use Interior Ministry vehicles and equipment - much of it bought with American money - to carry out revenge attacks against the minority Sunni Muslims, who persecuted the Shiites under Sunni dictator Saddam Hussein," he added.

Beginning in 2002, the administration's case for a pre-emptive war in Iraq was plagued by similar oversights, oversimplifications, misjudgments and misinformation. Unlike the administration's claims about the Samarra bombing, however, much of that information was peddled by Iraqi exiles and defectors and accepted by some eager officials and journalists.

The best known of those pre-war claims was that Saddam had weapons of mass destruction and had reconstituted his nuclear weapons program - Bush's primary stated reason for invading Iraq.

Administration officials and their allies also claimed that Saddam had trained terrorists to hijack airplanes; that a Saddam emissary had met with lead Sept. 11 hijacker Mohammed Atta in Prague; that Iraq had purchased aluminum tubes that could be used only to enrich uranium for nuclear weapons; that Iraq had attempted to buy uranium from the African country of Niger; that Iraqis would greet American troops as liberators; and that Iraqi oil revenues would cover most of the cost of the war.

The administration has continued to offer inaccurate information to Congress, the American people and sometimes to itself. The Iraq Study Group, in its December report, concluded, for example, that the U.S. military was systematically under-reporting the violence in Iraq in an effort to disguise policy failings. The group recommended that the military change its reporting system.

Whether many of the administration's statements about Iraq for nearly five years have been deliberately misleading or honest but gullible mistakes hasn't been determined. The Senate Intelligence Committee has yet to complete an investigation into the issue that was begun but stalled when Republicans controlled the committee.

On Thursday, frustration over the accuracy of administration statements on Iraq boiled over during Rice's testimony before the Senate Foreign Relations Committee hearing.

"Madam Secretary," said Sen. Bill Nelson, D-Fla., "I have supported you and the administration on the war, and I cannot continue to support the administration's position. I have not been told the truth over and over again by administration witnesses, and the American people have not been told the truth."

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