MISSION TO SUMATRA.

The United States military has a long and bitter history of being constrained by the countries that host its overseas military bases. Thailand in 1975 objected to U.S. Marines using Thai bases to stage their response to the seizing of the American freighter Mayaguez by the Khmer Rouge. Costa Rica in 1979 ejected a U.S. Air Force unit that was preparing to evacuate Americans from Nicaragua. And Spain and France in 1986 refused to let U.S. planes based in Britain fly over their territory on their way to bomb Libya. When the government of Turkey refused, in early 2003, to allow American forces to invade Iraq across the Turkish border, Pentagon planners got serious about freeing the United States from the sensitivities of allies. The technology already existed to resupply warships on the high seas. Reorganizing the Navy to do so as a matter of routine could mean never having to use foreign bases at all. As naval officers like to put it, "sea-basing" allows the United States to project its power anywhere in the world "without a permission slip." In the past two years, the Navy has also begun organizing what it calls Expeditionary Strike Groups--small fleets built around amphibious assault ships stuffed with marines and helicopters. The Navy has four such groups afloat now; it plans to have more patrolling international waters--"like a cop on the beat"--ready on a few days' notice not only to put marines ashore anywhere in the world but to support them for as long as they need to be there. Sea Power 21, the Navy's broad plan to respond to the post-9/11 era of small wars and uncertain alliances, is a military policy for a day when America might find itself without allies.

Rear Admiral Christopher Ames, the commander of Expeditionary Strike Group Five, learned about the Asian tsunami on December 26th the way most of us did: from television. He and his strike group--seven Navy and Coast Guard ships plus a submarine, carrying among them more than two thousand marines--had just left their home port of San Diego for a six-month deployment. The group was a couple of days from Guam, where it was scheduled to stop before heading for the Persian Gulf. The group's marines were the closest to the disaster scene, so, in anticipation of an order, Ames told his officers to begin planning to provide help to tsunami victims. "I had a feeling," he told me, as we talked in his cramped stateroom aboard the U.S.S. Bonhomme Richard.

Ames is no crusty old salt; at fifty, he has an eager, open manner that seems more executive than warrior, and a master's degree in public administration from Harvard's Kennedy School of Government. The formal order came by classified e-mail on December 28th to stop at Guam for supplies and then "proceed at best speed" to Sri Lanka. " 'Proceed at best speed' aren't words you often hear," Ames said. "We're very fuel conscious. An order like that is not given without considerable forethought." A few days later, the group was redirected to Banda Aceh, in Sumatra, the city closest to the earthquake's epicenter. As they pulled into Guam, trucks loaded with humanitarian supplies were lined up on the docks "as far as you could see," Ames said. He sent a party to the Ace hardware store near the port to buy just about everything in stock--shovels, lumber, hammers, nails--and within ten hours the group was under way again.

Expeditionary Strike Group Five was in many ways the perfect response to the tsunami. No other agency responding to the disaster had anywhere near its capabilities. The Bonhomme Richard alone would have been a godsend to the people of Sumatra. Commissioned in 1998 and named for John Paul Jones's privateer, she was designed to be the Marine Corps's dream boat. Her entire stern opens to release the high-speed air-cushion landing craft necessary for the Marines' rare but signature beach assaults. From the outside, she resembles a small aircraft carrier, though she lacks the catapult for throwing planes into the air. Instead, her flight deck is given over to six vertical-lift Harrier jump jets as well as a wide selection of helicopters, big and small. In addition to being a seaborne platform from which to launch land assaults, the ship could serve as a floating emergency ...