Head head-chopper Abu Musab al-Zarqawi had another close call recently; he escaped again, but this time he had to leave behind a computer with a “very big hard drive:” Zarqawi Eludes Capture; Computer Discovered.

Apr. 25, 2005 - Jordanian rebel Abu Musab al-Zarqawi — Iraq’s most wanted fugitive — recently eluded capture by American troops, but left behind a treasure trove of information, a senior military official told ABC News.

On Feb. 20, the alleged terror mastermind was heading to a secret meeting in Ramadi, just west of Fallujah, where he used to base his operations, the official said.

Task Force 626 — the covert American military unit charged with finding Zarqawi — had troops in place to grab the fugitive, and mobile vehicle checkpoints had been established around the city’s perimeter. Another U.S. official said predator drones were also in flight, tracking movements in and around the city.

A source who had been inside the Zarqawi network alerted the task force to the meeting. Officials deem the source “extremely credible.” The senior military official said that just before the meeting was scheduled, a car was pulled over as it approached a checkpoint. “Zarqawi always has someone check the waters,” said the official.

A pickup truck about a half-mile behind the car then quickly turned around and headed in the opposite direction. Officials now believe Zarqawi was in the fleeing truck. U.S. teams began a chase, but when the truck was pulled over several miles later, Zarqawi was not inside.

What the task force did find in the vehicle confirmed suspicions that Zarqawi had just escaped. The official said Zarqawi’s computer and 80,000 euros (about $104,000 U.S.) were discovered in the truck.

Finding the computer, said the official, “was a seminal event.” It had “a very big hard drive,” the official said, and recent pictures of Zarqawi. The official said Zarqawi’s driver and a bodyguard were taken into custody.

The senior military official said that they have since learned Zarqawi jumped out of the vehicle when it passed beneath an overpass, presumably to avoid detection from the air, and hid there before running to a safe house in Ramadi.

When Mr. Zarqawi's terrorist movement emerged in Iraq more than a year ago, intelligence analysts saw it as separate from Al Qaeda, with more ferocious rhetoric than the better-known terror group and a willingness to kill large numbers of Muslim civilians.

But now, the US and its allies face a grave and growing threat: an alliance of mutual interests and convenience between the group that carried out the 9/11 attacks in the United States and the one that has contributed so much to Iraq's chaos.

"There were certainly some differences between bin Laden and Zarqawi,'' says Rohan Gunaratna, a terrorism expert at Singapore's Institute of Defense and Strategic Studies. "But these differences were minor compared to the biggest things they have in common - their desire to hit at the US."

Mr. bin Laden's statement coincided with a devastating spurt of insurgent activity inside Iraq targetting IP (Iraqi Police) and Shiites.

For bin Laden, the advantages of the alliance are clear, says Mr. Gunaratna. The operational capabilities of Al Qaeda have been relentlessly trimmed back by the US since the attacks on Sept. 11, 2001, but he and most of his ideological core remain free.

Since the liberation of Iraq and especially so after the elections, Zarqawi and bin Laden has repeatedly called Iraq a battleground against the "crusader" West, even as Zarqawi has emerged as his principal agent. Zarqawi has positioned himself at the head of a growing network that US officials believe has been behind more than 70 car-bombings inside Iraq and "now makes him the de facto operational head of the Al Qaeda movement, not the Al Qaeda group, worldwide,'' says Gunaratna.

Zarqawi and his fighters were the target of the US siege on Fallujah last month. But US officials say they suspect many of the militants escaped Fallujah to other Sunni cities such as Mosul, which has been the scene of recent insurgent attacks.

By combining their resources, Zarqawi and Al Qaeda seem to be aiming to further amplify their message of total war against the US, the Middle Eastern regimes it favors, and Israel, with an expanded Internet reach and ongoing attacks against US and Iraqi forces.

The Sunni-Shiite split

Bin Laden's latest statement urged Muslims to attack the US and any Iraqis that work with the interim arrangements. In the two-minute, five-second audio tape, he referred to what he sees as "the third world war," led by the "Crusader Zionist Alliance" against Muslims who, in turn, "have a rare and precious opportunity to get out of the dependency and slavery to the West."

Zarqawi originally called his group Tawhid and Jihad, and his first statement of note in Iraq was peppered with venomous anti-Shiite attacks. Analysts once thought Bin Laden was unwilling to call for all out war between Shiite Muslims and Sunni Muslims, the dominant Muslim sect of which both bin Laden and Zarqawi belong.

Both men's Salafy branch of Sunni Islam is highly intolerant of Shiites, as is Saudi Arabia, but it had seemed that bin Laden wanted to keep the focus on the US. Zarqawi, for his part, seemed to want to form his own organization.

But what unites them both is their intense hatred of the US and all other non-Muslim nations. A trait they share with Saddam and with a billion and a half Muslims

Story Credits: ABC News, Martha Raddatz filed this report for "World News Tonight." and Christian Science Monitor