IT SEEMED A BIT THEATRICAL, but there was no reason not to take Larida at his word. Abu Sayyaf wasn't as strong as it had once been, but it could still muster enough fighters to overwhelm 84 lightly armed men. More apropos, if five years of recent history proved anything, it was that Abu Sayyaf and Americans made a bloody mix.

The group became notorious at the turn of the millennium, targeting tourists in the southern Philippines and East Malaysia. In 2000, Abu Sayyaf abducted 21 tourists and employees from a dive resort on Sipadan Island, releasing 20 of them months later for up to $25 million in reported ransom. On May 27, 2001, the group struck again. Three slight, camouflaged men bearing M16s burst into the beach cabin of Martin and Gracia Burnham, an American missionary couple celebrating their anniversary at the Dos Palmas Arreceffi, an exclusive resort just off the Philippine island of Palawan. The men forced the half-dressed couple onto the deck of a 35-foot speedboat and, after nabbing another American and 17 Filipinos, vanished into the Sulu Sea. Six days later they took four hospital workers, and two weeks after that they beheaded three of the hostages: a cook from the Dos Palmas, a security guard, and the third American, 40-year-old Californian Guillermo Sobero.

The Burnham kidnapping was picked up by news outlets, thanks to its tantalizing mix of vacationing Americans, sea pirates, and island paradise, but nowhere was Abu Sayyaf portrayed even remotely as a threat to national security. When it was first formed, in 1990 by Abdurajak Janjalani, a Filipino mujahedeen veteran who'd fought the Soviets in Afghanistan, Abu Sayyaf (Arabic for "Father of the Sword") was dedicated to fighting for a strict Islamic state in the southern Philippines. It was reportedly funded by Osama bin Laden's brother-in-law Mohammed Jamal Khalifa and trained by such veteran Al Qaeda leaders as Ramzi Yousef, the architect of the 1993 World Trade Center bombing.

According to U.S. intelligence, Abu Sayyaf remained a serious jihadist threat throughout the late 1990s, even after the death of Janjalani in 1998. I got a different picture from seven ex–Abu Sayyaf I interviewed on Jolo, including the group's former imam. After Janjalani's death, Abu Sayyaf had devolved into a criminal enterprise, they told me, with ransom windfalls going directly to his more secular-minded successors, Abu Sabaya and "Commander Robot." While Sabaya and other leaders spoke of jihad in public, the imam said, in private their aims were decidedly more temporal.

In November 2001, President Bush announced that the U.S. would send troops and aid to the Philippines, opening what the media came to call the "second front" in his war on terrorism. By spring 2002, Exercise Balikatan was in full force, with 660 U.S. Marines, Green Berets, and Navy SEALs—acting in an advisory role, as the Philippine constitution forbids foreign combat operations on its soil—joining the CIA and FBI personnel already in the southern islands. Using bugged cell phones, spy planes, double agents, and even a takeout pizza tracked by a drone armed with an infrared camera, the CIA took upwards of four months to locate the Burnhams and the remaining hostage, a Filipina nurse—the others having either been killed, freed, or ransomed. In the ensuing firefight between Abu Sabaya's forces and the Philippine army, Gracia Burnham was rescued; her husband, Martin, and the nurse died in the crossfire.

Up until about a year before I arrived, maneuvers on Jolo consisted largely of combat raids, with the Americans remaining on base while the Filipinos conducted battalion-size search-and-destroy sweeps backed by helicopter gunships and artillery batteries. The United States supplied Special Forces advisers, signals intelligence, and logistical support via the U.S. Joint Special Operations Task Force–Philippines (JSOTF-P), while the Filipinos provided the manpower and local knowledge. By mid-2003, a good number of Abu Sayyaf's core leaders were in prison or the grave.

But it was precisely during this low ebb that Abu Sayyaf was reborn on Jolo as a true international terrorist threat. With its leadership solidified under Khadafi Janjalani, the staunchly jihadist younger brother of the deceased founder, the group formed an alliance with Jemaah Islamiya, which had been all but forced out of Indonesia after the first Bali bombings. Using Jolo as their base, the terrorist partners struck back, launching new attacks, training operatives in scuba diving, and planning raids on resorts in Malaysia. In 2004, Jemaah Islamiya and Abu Sayyaf, working with a third, Manila-based group, sank the multistory SuperFerry 14 as it left Manila Bay, killing 116 Filipinos. It was the deadliest terrorist attack in Philippine history.