Yusniar still hears the roaring in her head, the waves thunderously loud. The sea that was supposed to be a mother, protecting, sustaining, became a fury, sweeping two of her children away.

Compared with some people, she was lucky. Yusniar, 50, was able to find them and bury them herself, before retreating to the hills where she can keep an eye on the ocean, keep it in its place, from her tent made of blue plastic sheets and Styrofoam fished out of the swamps. Neither she nor the 150 others camping with her near Banda Aceh, capital of the Indonesian province that suffered the worst destruction, are ready to come down. The relief workers haven't yet discovered them, like untold numbers of others. "The water took away everything," she says. "We're afraid the waves may come back and try to take the rest of us."

The most experienced soldiers in the modern wars against catastrophe call this the greatest challenge of their lifetime. The arrival of aid to the battered region offered the first promise of relief to the storm's survivors, but many questions remain: How quickly can $4 billion go toward saving 5 million people when the U.N. is warning that disease could kill as many as the tsunami did, a number now reaching upwards of 150,000? How do thousands of rescuers, from hundreds of agencies, from dozens of countries, speaking different languages, coordinate their efforts so that relief workers in need of antibiotics don't find that the truck they are unloading carries only biscuits and blankets? How do they resettle a port town when residents look at the ocean and see a grave, refuse to eat fish for fear it has fed on the lost? How do they calculate human nature in countries where government soldiers fight with rebels over who gets the credit for feeding people who are close to starving?

As if to rebalance some cosmic scale, another wave is washing over South Asia like none the world has ever seen. The worst disaster in memory has evoked the greatest outpouring of charity. "Just as we see the power of nature to destroy, we have seen the power of human compassion to build," said Britain's Chancellor of the Exchequer, Gordon Brown. The pledges coming in to the U.N. for tsunami relief already surpass all the relief money received in 2004 for the top 20 disasters combined. The politics of pity is never pure, so there was a kind of global competition in generosity, especially after the U.S. increased an early pledge of aid tenfold, to $350 million. Japan offered $500 million, Germany topped that with a $660 million pledge, and Australia weighed in with $810 million. Arab commentators engaged in some self-criticism, asking why Norwegians and Belgians offered so much more than Arabs to help Asia's suffering Muslims. During his visit to Indonesia, the hardest-hit country and the world's most populous Muslim nation, Secretary of State Colin Powell could not let pass an opportunity for self-congratulation. "I think it does give the Muslim world and the rest of the world an opportunity to see American generosity, American values in action," he said.

But for all the strutting and spitting, the overwhelming response was one of mercy. The money came so fast it crashed the website of Catholic Relief Services. Save the Children was logging more than 10 times the normal volume of calls, so that everyone from the CEO to the custodians was recruited to man the phones. Some groups, like M??decins Sans Fronti??res (Doctors Without Borders, or MSF), actually announced that they had taken in all the money they could use for tsunami relief and began directing donors to their general disaster funds, because other places in the world still need help even if they don't make headlines. But the charity toward the tsunami victims was unrelenting. Kids in Michigan sold hot chocolate; in North Carolina they sold lemonade; students in an eighth-grade class in Wenatchee, Wash., voted unanimously to give their class-trip money, which they had been raising for more than a year, to the Red Cross. There was Sandra Bullock pledging $1 million, Willie Nelson scheduling a benefit concert, NBA players offering $1,000 for every point they scored during games played late last week, and Helen E. McKenna, 88, a widow in San Francisco, donating her whole month's Social Security check. "My family was saying I was getting too old to handle my own money and that I should get a financial adviser," she said. "But it's my money. I can do whatever I want with it."
 
The same technology that has made this the most intimate of modern horrors has vastly increased the size and speed of the response. Relief organizations that used to have to wait for the check to come in the mail were receiving 80% to 90% of their donations online and moving the money out into the field faster than ever before. A dollar donated in the U.S. to Action Against Hunger, for example, is wired from New York City to the headquarters in Paris, where it buys water tanks, pumps, pipes, testing kits or chlorine tablets. Those supplies are shipped to international staging grounds in Igualada, Spain, near Barcelona, flown to Colombo, Sri Lanka, then trucked to a place like Batticaloa, on the island's northeast coast. Time elapsed from donation to distribution: 48 hours.

Raising the money is just the beginning. Delivering the supplies to the people who need them turned out to be the greater challenge. That meant confronting a practical, political and cultural obstacle course that slowed down aid to the most desperate areas while everyone learned the shortcuts. In many places, the roads that were bad to begin with are gone now and the ports swallowed whole. With bulldozers scarce, elephants have been enlisted to help clear debris. When pilots try to fly into a small airport, they find that the maps are suddenly wrong because the landscape has been rubbed away. Precious hours were lost when the lone airstrip in Banda Aceh was closed after a 737 hit a water buffalo while trying to land. "We need to make small, damaged airstrips some of the busiest airports in the world," says the U.N.'s Jan Egeland. In some Sumatran villages, it was impossible to deliver any goods at all until the U.S. and the Australian military showed up with amphibious vehicles that could stage beach landings. Sari Galapo, a U.N. volunteer in Batticaloa, was worried about the people on an island no one had heard from since the bridge to the mainland was washed out, so she set off by canoe. "The boat was barely above the water level, and I didn't want to look at the water," Galapo says. When she arrived, she discovered that the local government official had lost most of his family to the tsunami, become depressed, poisoned himself, and was hospitalized. In the meantime, no aid had got through until Galapo sounded the alarm.
 
When the physical hurdles are conquered, the political ones remain. In India, where 10,000 died and 6,000 are missing, the government was determined to portray itself as an advanced nation that can manage its troubles and made a point of dispatching its own relief workers to aid other countries in the region. The government was especially sensitive about foreigners invading the Nicobar islands, where the military keeps a secret electronic-listening post. Sparsely populated and almost impossible to reach in normal times, the islands are home to some of the world's last Stone Age tribes--five groups, with populations of 30 to 250, of Pygmy Africans and Mongol hunter-gatherers who stalk wild pig in the rain forest with bows and arrows. They were believed to have been wiped out by the tsunami, until a relief helicopter attempting to assess the damage was fired on by tribesmen shooting poison arrows.

Across the Nicobars, the International Red Cross estimates a death toll of 30,000 out of a population of 50,000. Meghna Rajsekhar, 13, saw the ocean swallow her mother and father, and after floating at sea for two days on a wooden door, she washed up on a Car Nicobar beach that was swarming with snakes. Newspapers wrote of refugees in Great Nicobar fending off crocodiles as they trekked through the jungle in search of water. For Aisha Majid, the tribal leader of Nancowry, an island filled with the homeless, the government's actions make no sense. She asks, "When the government can help other countries, why are they letting us down?" Says fellow survivor Aslam Majid, 22, who went five days without water: "People aren't dying from the tsunami. They're dying of thirst and hunger."

Elsewhere, relief workers have found themselves caught up in civil wars that have been raging for years. In Sri Lanka, there were hopes for some kind of peace, however temporary, between government forces and the Tamil Tiger rebels who have waged a 21-year war for independence in the northern part of the country. Scores of displaced Tamil families taking refuge in a school in Kudathanai had gratefully accepted food and water brought by government soldiers. But when soldiers arrived with a specially cooked New Year's meal, refugees refused it on orders from a rebel. That night part of the school was set on fire. "We are stuck between the army on one side and the [Tigers] on the other side," says K. Jayakumar, 29, a fisherman. "Please tell them both that we deserve some peace after all we have been through."
 
In all the worst-hit areas, the most immediate enemy is infection. Thousands of people were essentially attacked by their own flimsy homes, sliced up and gashed by falling planks of wood, shards of glass and jagged pieces of corrugated tin. So many wounds went untreated or were badly treated in local clinics that gangrene and tetanus have set in; amputation is the most common operation in field hospitals.

Among the first international aid workers to reach ground zero on the Indonesian island of Sumatra were the doctors and nurses of MSF. When they arrived at the one functioning hospital in Sigli, on the east coast, there was only a single, volunteer surgeon on hand. "Our hospital was crippled," says Dr. Taufik Mahdi, director of the 35-bed unit. "Most of our doctors and nurses were too traumatized to work or left to look for loved ones missing after the tsunami." That first day the MSF team performed six operations, and it hasn't stopped since. "The minute we sew one up," says Dr. Claire Rieux, a general practitioner from Paris, "another gets wheeled in."

Spending a day at the hospital with the MSF team reveals the scope of the crisis. "Oh, man, this one is really bad," an Australian doctor shouts as he approaches the operating theater. He's holding up the arm of a man whose limb looks like a shank of lamb. The elbow is essentially gone, and the lower and upper arm is barely held together by a few sinewy strings of muscle and flesh. Though paint is peeling off the walls and a layer of grime covers many of the hospital's windows, Sigli's only hospital is fairly clean compared with many others in Indonesia's remote provinces. There are small victories. A young girl is wheeled in for surgery, her left foot severed at the heel. The doctors fear they may have to remove her leg at the calf to stop the infection from spreading, but after a massive cleaning and huge doses of antibiotics, her foot is reattached.

Fran??ois Gillet, MSF's logistics coordinator in Sigli, is desperately trying to find extra beds, plugs and lightbulbs, which no one seems to have. "It's the little things that often get overlooked and are hardest to find," he says. The group has relied on satellite phones for most of its communications, but even they have been less than reliable. "This is why we have to be as organized as possible," says Belgian Alexis Moens, the field coordinator. "You have to put up a structure that is strong enough on both the medical and logistical sides. Otherwise, things just won't work."

Other relief workers operate as a mobile triage unit, moving through the refugee camps that have sprouted across Sumatra's now barren landscape. Some 50,000 people are camped in local mosques and schools. Most of the refugees are still using rivers for washing their dishes and bathing--a recipe for cholera and typhoid. As the advance teams uncover unsanitary conditions in the camps, they report them to MSF water and sanitation units working in the area. "We work until midnight every day at the earliest, but we're always running behind," says Moens. "We just don't have the time or people to be everywhere."
 
In a crisis of this scale, some tasks require the kind of muscle only a superpower has. The U.S. Navy has 21 ships and 12,600 crew members working on rescue and relief operations in the waters off Indonesia, Thailand and Sri Lanka. Seahawk helicopters--their blades filling the air with a fluttering rumble--sidle in and touch down on the U.S.S. Abraham Lincoln's 4 1/2-acre flight deck. Since sunrise on Jan. 1, the carrier's Seahawks have been flying from 13 to 17 missions a day. "We're going nonstop from dawn until sunset. Then the commanders meet, talk about what we've learned that day and map out what needs to be done tomorrow," says Captain David Lausman, the ship's executive officer.

The sailors and pilots are trying as best they can to coordinate with private groups to set up a smooth supply line. A host of aid organizations flies in supplies on U.S. C130 cargo planes to the tiny runway of the airport at Banda Aceh. Once unloaded, the planes must take off immediately to clear space for the next plane. The Seahawks, meanwhile, are landing on a converted football field a few hundred yards away, and the pilots are managing the transfer of supplies from the C130s to the helicopters. "It was like the Wild West down there when we first flew in," says Lieut. Dave Moffet, "but it's getting better." The helicopters head off for the villages, each one delivering 2,000 to 3,000 lbs. of food, medical supplies, communications equipment and even a few toys and some candy for the children. Along the way, their crews scour the countryside, looking for isolated hamlets that have yet to receive help and for displaced people straggling along roads. When they come across those who are sick or wounded, they ferry as many as possible to the field hospital. "We're seeing a lot of dehydration, diarrhea, lacerations and people missing limbs," says Kenny Rowe, a petty officer on a Seahawk. "We've got people with gangrene and other infections that could be fatal that haven't been treated for a week." Back at the airport, a few C-2 Greyhound transport planes load up with rice and carry it in. "Right now rice is gold to these people," says Rowe.

But like the doctors on the ground, the pilots encounter frustration. "We land in villages, and we can't understand what they're telling us," Moffet says. "People tell us there's a village 6 kilometers away that needs food, and then we go out looking for it and can't find it, and we have to go back two or three times looking for it." Desperate people rush the helicopters and risk being sliced by the blades. "We're lucky most of them are pretty short," he says with a wan smile. Now they try to get a translator off the choppers first to keep villagers back. "We try and fly different routes every day to find villages we're missing. We found one today because they had laid out an H in a field with white stones."
 
The Lincoln will eventually have to be relieved, perhaps by the U.S.S. Kitty Hawk. But for now, no one is in a hurry to see this tour of duty end. "Frankly, I don't care how long we're here," Moffet says. "We're not going to leave these people hanging." Sailors on the Lincoln receive constant emails from buddies elsewhere offering to pitch in.

The true test will come when attention wanes and the world moves on to some other preoccupation. The people in this region will need help for some time to come--and not just food, water and medicine. "They've lost everything. You'd be surprised--they need little things we don't even think about in our daily lives," says Gail Neudorf, deputy director of emergency and humanitarian relief for CARE USA. "Things like soap, washing powder, buckets, bottles for water so you have a clean container to keep water in, cooking utensils, sleeping mats, clothing, blankets, diapers, sanitary pads, matches, candles, lanterns, cooking fuel. In time, we'll look at getting books for kids out there, school kits." Then the survivors will need another army of donors to piece together the lives they have lost.