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SUSAN ROESGEN: And now this CNN exclusive. With the largest U.S. military operation since the invasion of Iraq in full swing, there appears to be emerging signs that America is fighting yet another enemy.

CNN'S Michael Ware now with exclusive details on how a manhunt for the people who ambushed and killed U.S. soldiers led the military down an unexpected path. Michael?

MICHAEL WARE, CNN CORRESPONDENT: Yes, Susan. What could be a worrying development for the Middle East is that the American military has now realized it's fighting even more enemies in Iraq than it ever knew.

We can reveal to you in this breaking story that the U.S. military says that it has captured a senior special operations officer here in Iraq from Lebanese Hezbollah.

This is the guerrilla organization that fought the Israeli defense force to a standstill in last summer's war in Lebanon. The U.S. military says that this special operations officer from Hezbollah was sent here to Iraq by Iranian forces, to help build and guide paramilitary fighters in this country, to attack and kill American soldiers.

Indeed, when they arrested this man back in March, and he eventually confessed, the U.S. military intelligence sources claim that it's now become clear that this Hezbollah figure played a crucial role in the attempted kidnapping of five American soldiers in January here in Iraq that ultimately led to those soldiers' executions.

Now, according to our intelligence sources and military sources, this Hezbollah leader and the Iraqi commanders he was working with have all admitted that they were part of a broad program being conducted by Iran's Revolutionary Guards Corps here in Iraq to destabilize the American mission by killing American troops. Susan?

ROESGEN: Michael, can you tell us anything about how this Hezbollah officer was captured?

WARE: Yes, I can. After the attempted kidnap of the five American soldiers in January, the order came down from top American commanders to hunt down the men responsible, and to kill or capture them.

Now, just a few weeks ago, U.S. and Iraqi forces killed the man during a raid whom they described as the mastermind who led the attempt to kidnap the soldiers.

Now, during the course of their investigation, they identified the top Iraqi militia leader who commands the feared "special groups," who'd authorized the attempt to kidnap the Americans, just like Hezbollah did with the Israeli soldiers, to spark last summer's war.

When they grabbed him, they grabbed the Hezbollah commander. They didn't realize it, though, because for weeks he played the role of a deaf mute. When his cover was blown, he eventually confessed.

ROESGEN: Wow, what a story, Michael Ware with an exclusive CNN report for us today. Thank you, Michael.

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SUSAN ROESGEN: Coming up, the war in Iraq and the war on terror has gotten even tougher for U.S. forces.

(BEGIN VIDEO CLIP)

MICHAEL WARE, CNN CORRESPONDENT: The American military has now realized it's fighting even more enemies in Iraq than it ever knew.

(END VIDEO CLIP)

ROESGEN: CNN's Michael Ware has the exclusive story on a new enemy in the war zone.



SUSAN ROESGEN: And now this CNN exclusive. With the largest U.S. military operation since the invasion of Iraq in full swing, there appear to be emerging signs that America is fighting yet another enemy. CNN's Michael Ware now with exclusive details on how a manhunt for the people who ambushed and killed U.S. soldiers led the military down an unexpected path.

(BEGIN VIDEOTAPE)

MICHAEL WARE, CNN CORRESPONDENT (voice-over): These men are masters of guerilla warfare: Lebanon's Hezbollah. Last year, they claimed victory over the might of the Israeli Defense Force. Now believed to be fighting another war in Iraq.

U.S. intelligence sources say they have captured one of Hezbollah's top special operations commanders, Ali Musssa Daqduq. Said to be an expert with these roadside bombs, his role in Iraq was so covert, there are no known pictures of him here, save for his prison mug shot and a confession, which coalition forces have not released. Captured on March 20 in the southern city of Basra, the Americans say he and the Iraqi militia commanders he trained and led admitted working with Iran's elite Quds Force special operations unit.

Documents, forensic evidence, and the personal effects of dead American soldiers seen by members of the Iraqi government and shown to CNN support their claims. After months of interviews with Shi'ia militia members in Iraq, as well as Iraqi government and intelligence officials, CNN sought the U.S. military's comments on the arrests, but the military declined.

However, senior U.S. intelligence officials say their confirmation of Hezbollah's long rumored involvement in Iraq began with the January 20 attack on American soldiers in Karbala, a well-planned attempt to kidnap five GIs that went horribly wrong, ending with the soldiers' execution.

Senior U.S. military officials tell CNN that after the attack, the order came to hunt down the men responsible and kill or capture them. That mission has been a stunning success. A few weeks ago, during a raid in Baghdad's Sadr City slum, American and Iraqi forces killed this man, Azar al-Dulaimi, said to be the mastermind who led the Karbala attack. While Mehdi army militiamen mourned his death in this memorial in Sadr City filmed by CNN, coalition operations across the country had already seen most of those behind the kidnap attempt killed or imprisoned.

Early results in the U.S. investigation led to this man, Qais Khazali, seen here in 2003 when he was the spokesman for rebel cleric Muqtada al-Sadr's Mehdi army. By the time of his March arrest, he had left the Mehdi army and come to head one of the most feared organizations in the country, known as the "special groups," a well-trained, well-financed and efficient paramilitary unit modeled on Hezbollah. And according to U.S. intelligence sponsored by Iran's Quds Force, a claim Hezbollah's Daqduq and the Iraqi leader Khazali have apparently admitted during their interrogations.

Looking for Khazali, the coalition troops found more than even they had hoped: computer documents detailing the planning, training and conduct of the failed kidnap. What they didn't know is they had also scooped up Hezbollah's advisor to the Iraqi "special groups." Originally pretending to be deaf and mute, Daqduq's real identity was not revealed for weeks. Once uncovered, though, American officials say he began to talk.

The Americans now believe his role was crucial to the Karbala attack. What remains a mystery is why Lebanese Hezbollah's leadership would risk sending advisors to Iraq. American intelligence officers suspect Hezbollah had no choice - indebted to Iran's Quds Force for its decades of military and financial support.

Contacted by CNN, a Hezbollah spokesman in Lebanon said he would not dignify the U.S. allegations with a response. And though representatives of Iraq's Mehdi army militia and cleric Muqtada al-Sadr say they share some of Hezbollah's ideals, they deny receiving any military aid.

"I say clearly that we do not accept any logistics, financial, or any other kind of support from anyone outside the borders of Iraq," says this advisor to Sadr. The Iraqi government declined to comment. And though Tehran has repeatedly denied arming or aiding any militia forces in Iraq, Daqduq's arrest and the weight of Washington's new evidence of Hezbollah's presence in Iraq may just demand fresh answers from Iran.

Michael Ware, CNN, Baghdad.