They've been calling them "war games" to get around concerns that the return of US troops to the Philippines may violate the nation's Constitution. But in testimony to the Philippines house this week, Defense Secretary Angelo Reyes was clear about the intentions of the exercise, which began yesterday: Destroy the Abu Sayyaf, a militant Islamic group with historic ties to Al Qaeda.
Some 150 US special forces officers will help lead Filipino soldiers on training patrols in Basilan, the militant Islamic group's stronghold, and about 500 other American soldiers will play a backup role. The US will supply night vision goggles, helicopters, and sophisticated spy equipment that patrols will use as they fan out over the verdant hills of this Los Angeles-size island.
As the US expands its military campaign beyond Afghanistan, the return of American soldiers to the Philippines - a former colony that closed the last American bases here nearly a decade ago - is also making some Filipinos uneasy.
They worry about sovereignty, specifically language in the Constitution about not allowing foreign troops to fight here. And some are uncomfortable that the government had to appeal to its old big brother, the US, for help in cleaning up a domestic mess.
One government source, requesting anonymity, wonders if the US "doesn't trust the competence of the Philippine army to eliminate the Abu Sayyaf," despite having "nine battalions to fight 70 to 80 Abus."
"To us who've been living here, Abu Sayyaf is simply a local problem, to be dealt with by local authorities," says Edgar Araujo of Western Mindanao State University. "If the problem is the military, rebuff the military - don't bring in foreign troops."
Mr. Reyes yesterday defended the exercises as being in the Philippines national interest. "We are not going to allow the United States to impose its will on us and ... [be] coerced into doing anything against our national interest,'' Reyes told the House.
To be sure, Philippine public opinion is overwhelmingly against the Abu Sayyaf, with a recent poll showing 84 percent public approval for US military assistance in wiping the group out.
But some people are concerned that the US campaign here won't stop with Abu Sayyaf - an issue that could bring grave domestic political implications.
The communist New People's Army, a clandestine organization that has committed a number of terrorist acts over the years, threatened in a statement issued Wednesday to attack US troops and others in the country in response to the deployment, which the NPA called an act of "US aggression." Also on Wednesday, an American hiker on Mount Pinatubo was presumed killed and his German companion injured by unidentified gunmen. The police suspect it was a communist attack.
The Moro Islamic Liberation Front (MILF), which has been fighting for independence in the Southern Philippines for 20 years, is currently trying to rekindle on-again off-again peace talks with the government.
Some analysts worry that US attention may shift to the MILF - which has thousands of members and a politically sophisticated leadership - because of the recent connection of a man described as an MILF trainer with a plot to blow up the US Embassy in Singapore.
The US has thus far kept its comments about the Philippines entirely focused on the Abu Sayyaf. During the six-month mission, the US soldiers will operate under Filipino command, and will only fire in self-defense.
The US interest in the Abu Sayyaf is both practical and emotional. The group has held an American couple, Martin and Gracia Burnham, hostage for eight months since snatching them from a beach resort in the south, and the Burnhams' plight has become an issue of intense focus in Washington.
Practically, the Abu Sayyaf are the world's easiest group with ties to Al Qaeda to go after.
For one thing, the Philippines is overwhelmingly Catholic. In neighboring Indonesia, the government has been slow to move against alleged terrorists for fear of a backlash among its majority Muslim population.
"I'm giving my qualified support [to the US mission], as long as they confine it to their stated mission" says Gerry Salapuddin, Basilan's elected representative, and speaker of the House of Representatives. "Even the Muslims of Mindanao don't want the Abu Sayyaf. They have painted a bad image of Islam."
And the group has a strong historical link to Al Qaeda. The Abu Sayyaf's deceased founder, Abdurajak Janjalani, fought against the Soviet invasion of Afghanistan. In the early 1990s, Philippines intelligence officials say Mohammad Jamal Khalifa, a brother-in-law of Osama bin Laden, funded the group and facilitated the visits of Al Qaeda trainers.
Though officials here say those contacts have been dormant since at least the mid-1990s, the concern that they could be rekindled has been enough to pique US interest.
Mr. Araujo cautions the US to keep its campaign focused on Abu Sayyaf. "There are so many actors here, and now you factor in the United States. You start a fire, it can quickly transform into an inferno."
Chris Johnson contributed to this report from Basilan Island.