In the midst of the chaos that would ensue, the attackers would turn their attention to the U.S. Embassy, the primary target and a long-sought prize for the organization that investigators say provided critical support for the scheme: al-Qaeda’s affiliate in Iraq. Using the terrorist group’s expertise and weapons from Syria’s civil war, the plotters planned to rain mortar shells on the American compound and homes nearby.

“They wanted to kill as many as possible — Muslim and Christians,” said a Jordanian government official, speaking on the condition of anonymity to discuss an ongoing probe into the most serious terrorist plot uncovered here in nearly a decade.

Jordanian authorities foiled the plot last month, arresting 11 men said to be the ringleaders. Although the suspects are Jordanians, the investigation has affirmed the key role played by al-Qaeda’s Iraqi branch, commonly known as AQI, which analysts say is rebounding after being all but destroyed by U.S. troops in the past decade.

New evidence shared by security authorities here, including intercepted e-mails, shows that the terrorist cell received guidance from AQI. The instructions included recipes for powerful explosives intended to blow up shops, restaurants and embassies, according to Western and Middle Eastern officials briefed on the investigation.

The same kinds of explosives also are turning up in Syria, intelligence officials and terrorism experts say, underscoring AQI’s expanding role in that country’s 20-month-old civil war.

“What we’re now seeing is al-Qaeda in Iraq’s revival, not only as a movement in that country but as a regional movement,” said Bruce Riedel, a former CIA counterterrorism expert who is with the Brookings Institution. From its base in the Sunni provinces west of Baghdad, AQI appears to be attempting to rebuild old networks into Syria and Jordan “at an alarming rate,” Riedel said.

Equally worrisome, analysts say, is Syria’s emergence as a training ground for Islamist fighters from outside the country, including some who are linked to AQI. A Western intelligence official familiar with the Amman plot said most of the suspects had fought in Syria before returning to Jordan with new skills and a changed perspective toward their native country.

“They already were true believers,” the official said, “and they came back to Jordan seeing their own country through the same eyes with which they viewed the regime in Syria.”

The reemergence of AQI comes at a time when U.S. officials and analysts are expressing growing concern about other al-Qaeda affiliates, including al-Qaeda in the Arabian Peninsula, which operates in Yemen, and al-Qaeda in the Islamic Maghreb, which operates in North Africa. U.S. intelligence officials have said that some of the fighters involved in the Sept. 11 attack on the American diplomatic outpost in Benghazi, Libya, were associated with the North Africa branch.

The Western intelligence officials and most others interviewed for this article declined to speak on the record while discussing the ongoing terrorism investigation.

Ties to Salafi movement

The Jordanian plot, revealed by the kingdom’s officials on Oct. 21, is described as the most ambitious in the country since Nov. 9, 2005, when suicide bombers linked to AQI simultaneously struck three Amman hotels, killing 60 people and wounding more than 100. In a nod to that attack, the leaders of the new Jordan cell christened their plot “9/11 the Second,” a reference to Nov. 9, using the day-month format common outside the United States.

In interviews over several days, Jordanian officials said the scheme was hatched during the spring and summer by 11 Jordanians connected to the Salafi movement, an ultraconservative, puritanical sect within Sunni Islam with growing numbers of followers throughout the Middle East.

One Jordanian government official briefed on the plot described the cell members as casual acquaintances who bonded after volunteering as jihadist fighters battling government forces in Syria. He said the men, who were in their 20s and 30s, had crossed into Syria multiple times, gaining extensive fighting experience and weapons training.

“They are real fighters,” the official said. “From Syria, they had weapons training and tactics. They were good at shooting, and they knew how to use complicated communications systems.”

They also had another important advantage: easy access to the almost endless supply of weapons in Syria, where arms bound for rebel fighters arrive daily across the Turkish border. Cases of TNT, mortar shells, grenade launchers and even belt-fed machine guns were smuggled into Jordan for an attack that planners hoped would wreak havoc across the capital and lead to the collapse of the country’s Western-backed government.

The objective, according to an internal Jordanian report summarizing the plot, was to “cause chaos and anarchy and spread fear among the population, setting the stage for further operations to follow.”

A blueprint drawn up by the group, and later reconstructed by Jordanian counterterrorism officials, called for three distinct waves of attacks in Amman. The terrorists would open with coordinated bombings of two of the capital’s largest shopping centers, followed by strikes on luxury hotels frequented by diplomats and tourists.

With the city’s police occupied at those locations, the attackers would launch the main assault on the U.S. Embassy and the city’s affluent Abdoun district. They planned to hit the American compound and surrounding streets with bombs, sweeping machine-gun fire and a torrent of mortar shells, officials briefed on the plans said in interviews.

To build the biggest bombs, the Jordanians received vital help from AQI, including a formula for enhancing the explosive power of ordinary TNT, the officials said. The instructions were passed via e-mails, and the key ingredients were delivered to a safe house in Syria.

“They were planning to bring it in two nights before the operation was to take place,” the Jordanian government official said.

A prime target

The pickup never took place. As the plotters prepared to move to an operational phase, they were under constant surveillance by Jordanian intelligence operatives who had penetrated the cell and monitored its communications. All 11 suspected cell members were rounded up in mid-
October, along with a cache of machine guns, ammunition, explosives and forged documents.

Computers seized from the accused further documented the links to Iraqi terrorists, who appeared to view the Jordanian scheme as a long-sought opportunity to strike a blow against the Amman government and its ally United States, Jordanian officials said.

The dismantling of the terrorist cell will probably only reinforce Jordan’s status as a prime AQI target, Western intelligence officials and terrorism experts say. And, as Syria’s civil war continues, it is likely that new cells of radicalized, battle-
hardened jihadists will emerge.

With the arrival of ever-larger numbers of foreign jihadists, Syria is emerging as a base for training and a launchpad for operations for the Iraqi terrorist group, said Bruce Hoffman, a former counterterrorism scholar-in-residence at the CIA and a professor at Georgetown University.

“You have a well-developed infrastructure that is only getting stronger,” Hoffman said. “It’s not like the ‘underwear bomber,’ where al-Qaeda enlists amateurs in sophisticated terrorist operations. You’re talking about people with experience — perhaps not the ‘A Team’ but close to it.”

Moreover, Hoffman said, Syria is adjacent to al-Qaeda’s foremost nemeses in the Middle East: Israel, which finds itself increasingly besieged and isolated in the region, and Jordan, which Islamists view as more vulnerable in the wake of the Arab Spring uprisings.

“Luckily, this last attempt was foiled,” Hoffman said. “But al-Qaeda will continue to play the odds, with the hope that eventually they will succeed.”