Just before Soraya Tampalan, a 13-year-old Filipina who was born with a disfiguring cleft palate, was to undergo corrective surgery aboard the U.S. Navy hospital ship Mercy, she said she was a little nervous, then gently began to cry. Asked why, Soraya said: "I want to look pretty."

Several hours later, a team of U.S. military doctors, Navy Capt. Craig Cupp, Air Force Maj. Richard Buck and Navy Lt. Cmdr. Graig Salt, said the operation had been successful. Chief Petty Officer Don Bray, a Navy journalist, reported that Soraya, who had dropped out of school because other children taunted her, had said: "I want to go back to school and get an education."

The operation to correct Soraya's cleft lip has been but one of perhaps 50,000 procedures the medical crew aboard Mercy have performed in recent weeks in Southeast Asia. They have treated goiters, examined eyes for glasses, soothed burns, set broken bones, pulled rotten teeth and given all manner of shots. Another team removed cataracts that had blinded Mara Harun, 60, for seven years.

Doctors and nurses have taught classes and seminars with local medical people. Mercy's technicians have repaired respiratory ventilators, anesthesia machines, X-ray equipment and operating room lights in antiquated clinics in the Philippines, Bangladesh and Indonesia. Seabees from Navy construction battalions have fixed generators, repaired roofs and painted hospitals.

Not all have been successful. Four children with cleft palates had to be turned away because respiratory ailments precluded operations. Cancer patients could not be treated because that takes months. A Navy doctor, Cmdr. Lynn Leventis, who had not seen a maternal death in 15 years, witnessed two Bangladeshi mothers die from infection after they had delivered their babies.

Soraya Tampalan, Mara Harun and hundreds more were treated aboard Mercy when the ship was anchored off the island of Jolo, in the southwestern Philippines. Jolo is in the nation's poorest province, where 63 percent of the people live in poverty, and the average lifespan is 52 compared with the national average of 72.

Moreover, Jolo is in a region where a large majority of the people are Muslims. That chain of islands has been identified by U.S. intelligence as a route over which Muslim terrorists move among the Philippines, Indonesia and Malaysia. Similarly, Bangladesh is dominated by Muslims and Indonesia is the world's largest Islamic nation.

Mercy is part of a U.S. effort to persuade Muslims not to support terrorists.

Adm. Gary Roughead, who commands the U.S. Pacific Fleet and exercises operational control over Mercy, asserted that the 70,000-ton ship "is the most capable hospital on the planet — and you can move it around."

"What Mercy does," he said, "is to allow a force of good to go someplace, do good work and show people that there are alternatives to some of the forces that are in play in their part of the world."

Planning for Mercy's five-month voyage from its home port in San Diego began almost a year ago after the ship returned from assisting victims of the Indian Ocean tsunami in December 2004. That experience showed that many non-governmental organizations, having worked in Southeast Asia, could provide valuable knowledge of the region.

Several were invited to join the voyage. Aloha Medical Mission of Honolulu seeks to help people who lack access to medical care, and Operation Smile's volunteers repair facial deformities in children. The U.S. recruited military medical teams from Canada, India, Singapore and Australia and worked with those of the Philippines, Bangladesh and Indonesia.

Security was a constant concern. The ship often stayed offshore not only because port facilities were inadequate but to fend off potential assaults. Helicopters and two motorboats, Bandaid One and Bandaid Two, ferried medical people ashore and patients to the ship.

The Navy doctor who commands the medical teams, Capt. Joseph Moore, pointed to the need to win the trust of people who had never seen a ship as large as Mercy or flown in a helicopter or been attended by such a diverse collection of men and women, Americans and Asians, military people and civilians.

In a message to all hands, he said: "We were all witness to the courage and trust it took on the part of a Bangladeshi mother or father to escort their child through the surgical process. After a 30-minute transit from shore, they stepped out of the helicopter and onto the deck of this immense ship, and proceeded to walk into what must have felt like a completely foreign world."

Richard Halloran is a Honolulu-based journalist and former New York Times correspondent in Asia. His column appears weekly in Sunday's Focus section.