U.S. and British intelligence officials expected that when the invasion of Iraq began, division-size Iraqi units might surrender to coalition forces. But those defections never happened, and the mistaken forecast was one of the few real blunders of the Iraq war.

Behind this intelligence failure stands a decade-long effort to encourage a military coup in Iraq. For much of that time, the secret coup plot was known within the CIA by the cryptonym "DBACHILLES." Now, with Saddam Hussein's regime deposed, U.S. and Iraqi sources have provided a detailed account of a coup strategy that never delivered.

"There were suggestions that large parts of the Iraqi armed forces might well come over at the appropriate moment," confirms one key intelligence official. "It didn't happen in the way we hoped or encouraged." This official says that "there may well have been" a systematic effort by Hussein's intelligence services to deceive the United States, but the evidence is inconclusive. The botched coup efforts carry some important lessons for the present. They show how easily Iraqi intelligence penetrated these operations. And they illustrate the damage caused by a long-running feud between Iraqi exile groups and their patrons in Washington.

The DBACHILLES debacle began in 1994. The CIA around that time appointed a new head of its Near East Division named Stephen Richter, whose identity was long ago published. He and a former Army officer who headed the agency's Iraq task force believed that a military coup against Hussein was possible.

The CIA's new Iraq team is said to have met soon afterward with Gen. Mohammed Abdullah Shawani, a former commander of Iraqi Special Forces. A Turkmen from Mosul, Shawani had many contacts in the Iraqi military, including several sons still in uniform. Shawani's name has previously been published, too.

As the CIA was drafting its plans, the British encouraged the agency to contact an experienced Iraqi exile named Ayad Alawi, who headed a network of current and former Iraqi military officers and Baath Party operatives known as Wifaq, the Arabic word for "trust."

Complicating the CIA's coup planning was a similar effort in northern Iraq by Ahmed Chalabi's Iraqi National Congress. A CIA officer named Bob Baer was dispatched in January 1995 to coordinate the various covert efforts, but they only got more tangled. Chalabi launched his unsuccessful coup in March 1995, and Baer was suddenly summoned home to Washington.

The 1995 fiasco only reinforced the CIA's belief in the traditional military coup approach of DBACHILLES. But an Iraqi source argues that by late 1995, some of Shawani's and Alawi's operatives were already controlled by Iraqi intelligence.

Chalabi was so convinced that the military-coup plan had been compromised that he traveled to Washington in March 1996 to see the new CIA director, John Deutch, and his deputy, George Tenet. He told them the Iraqis had captured an Egyptian courier who was carrying an Inmarsat satellite phone to Shawani's sons in Baghdad.

When the CIA officials seemed unconvinced, Chalabi went to his friend Richard Perle, a prominent neoconservative. Perle is said to have called Tenet and urged that an outside committee review the Iraq situation. But the coup planning went ahead.

DBACHILLES collapsed in a blood bath in June 1996. The Post had run a front-page story on June 23 describing Alawi's role in "the latest CIA-backed plan" that was based on "contacts at high levels of the Iraqi military."

The Iraqis are said to have begun arresting the coup plotters three days later, on June 26. At least 200 officers were seized and more than 80 were executed, including Shawani's sons. Top CIA officials blamed Chalabi for exposing the plot, and the recrimination has persisted ever since.

As the Bush administration began planning its own Iraq policy, it inherited this tormented history. There was still a strong argument for a traditional military coup, with operatives recruited through the Iraqi tribal network. Indeed, in this column I endorsed Alawi and his strategy last year.

In the run-up to war, both Alawi and Shawani played important roles in the coalition's effort to encourage Iraqi officers to surrender or defect. It was, in essence, the same strategy that had been tried unsuccessfully in the mid-1990s, but intelligence operatives moved ahead, regardless. The anticipated defectors included a top Iraqi Defense Ministry official and a top Republican Guard commander. Among the few who were dubious from the start, it's said, was Defense Secretary Donald Rumsfeld. "Rumsfeld always said that you need to be wary of people who say they'll flip for you, because they're probably playing, at a minimum, both sides and saying similar things to Saddam," recalled Deputy Defense Secretary Paul Wolfowitz in an interview a week ago. "Rumsfeld was always skeptical of those claims, and it was justified."