PORTABLE PENTAGON

To most Americans, the prospect of returning home from a hot, dusty military base in the middle of the Qatari desert would bring feelings of pure, unadulterated joy. But for Edward Northrop, the emotions are more complex. Sure, he's eager to get back to his house in Tampa and his wife of some 20 years. But as he looks over the top of his gold, wire-rimmed glasses at the faces in front of him, he keeps getting choked up. Saying goodbye to these folks won't be easy, especially not now.

For the past seven months, Mr. Northrop has been the Protestant chaplain at Camp Asayliyah, the American base 20 miles outside the Qatari capital of Doha. When he first arrived he could count his congregation on his fingers and toes, but on this, his final Sunday, perhaps 150 or more are crowded into an auditorium that still smells of sawdust and paint. That kind of growth is partly the result of the chaplain's hard work-and partly the president's hard choices.

As the Bush administration mobilizes for war with Iraq, the numbers at Asayliyah have swelled dramatically, helping to transform an obscure supply depot into the U.S. military's Middle East nerve center. From here, some 700 miles south of Baghdad, Gen. Tommy Franks and America's top brass will make the strategic decisions that affect more than 150,000 troops on the ground. In other words, this is where the war will be thought, not fought.

It's no accident that Camp Asayliyah doesn't look like much from the road; passing motorists can see almost nothing of the base. After a bombing at the Marine Corps barracks in Beirut that claimed 237 lives, military planners began designing bases with generous set-backs from public roads. At Asayliyah, a half mile of empty desert serves as a buffer between the perimeter fence topped with razor wire and the core of the base, where several thousand soldiers eat, sleep, and plan for war. Even a suicide truck bombing at the entry gates would be unlikely to harm the personnel in the heart of the base.

Trucks on the inside are another matter, of course. Every day, local Arab drivers pull dozens of vehicles up to Asayliyah's front gates, loaded with computers and communications equipment, the materiel of modern warfare. Deep in a hostile part of the world, American troops regard every delivery as suspect. Drivers weave slowly through a zig-zag course of 8-foot-tall concrete barriers before reaching a tall metal canopy that serves as an inspection point. Armed guards check the drivers' papers, then make them stand aside while every inch of their vehicles is checked by hand.

When every truck, every box, is a potential bomb, security work along the perimeter is highly dangerous-so dangerous, in fact, that it's turned over to outside companies under contract to the U.S. military. A bombing on the perimeter would be tragic but not strategic, because any loss of life would come mainly from civilian ranks. Such is the calculus of life and death here in the desert.

Even at close range, past the barriers, the checkpoints, and the gun-toting guards, Asayliyah still appears to be the supply depot that it once was. Some three dozen warehouses, each about 100 yards wide by 250 yards deep, are scattered across the flat, sandy terrain. The scene looks at first like any industrial zone in any American city, except that each warehouse is surrounded by more of the 8-foot barriers and flanked by low, concrete bunkers piled high with white sandbags.

Nearly every aspect of life at Asayliyah takes place inside the metal-and-masonry warehouses. Outside the air-conditioned buildings, Qatar is a harsh and inhospitable place, despite the government's official welcome to American troops. Though cool Gulf breezes turn the city of Doha into a popular beach resort during the winter months, the inland desert can be uncomfortably hot even in February. From April to October temperatures rarely retreat from the triple digits, and punishing sandstorms can reduce visibility to zero.

Even without the sandstorms, the desert is visually disorienting. In the constant, hazy heat, the sky turns grayish-white like the sand, sucking all the color from the landscape and obliterating the horizon.

Life inside the warehouses can be equally disorienting. Soldiers work up to 19 hours a day, catching a little sleep whenever they're able. Inside the hushed, windowless warehouses where they live, day and night are indistinguishable. Soft amber lighting glows round-the-clock, creating a sort of permanent twilight.

Soldiers live in two types of housing, depending mostly on their rank. Some warehouses hold large white tents supported by pegs drilled into the concrete floors. With up to 88 people per tent, the living arrangements are necessarily spare: a twin bed, a narrow locker, and a small table for each occupant. Soldiers personalize their space however they can-a leopard-print bedspread here, a Washington Redskins pillowcase there-while they compete for coveted privacy partitions built by the Seabees, the Navy's construction crew, as time allows.

Across the street, higher-ranking officers are warehoused differently. They sleep two-by-two in metal shipping containers that have been converted into a sort of modular dorm room. At roughly 8 feet wide by 19 feet long by 7.5 feet tall, the containers don't offer much more square footage per occupant than the tents, but they do boast a TV and VCR, plus lights that can actually be turned off for sleeping and doors that can shut out the world. With containers stacked two high and connected by walkways of metal grillwork, the warehouses look more like a cellblock than a hotel. Still, this is the housing of choice, and younger officers dread the day they're displaced to the tents by the ever-increasing number of senior brass.

Most of Camp Asayliyah is top secret and closed to the media, but one of the warehouses was designed specifically to welcome the world's press. A state-of-the-art media center, housed well away from the command-and-control buildings, offers rows of televisions, scores of Internet hook-ups, and microwave transmitters for beaming communications around the world.

The 10 public information officers assigned to Asayliyah are girding to handle up to 3,000 credentialed media representatives who are expected to descend on the base if war does break out. In that case, the auditorium where Mr. Northrop preached his farewell sermon will become a common sight in the world's living rooms: When the Bibles and candles are put away, the auditorium will be transformed into Gen. Franks's media briefing room.

Mr. Northrop hopes it never has to come to that. "I'm still praying for a miracle," he says. "Most people around here are. But if no miracle occurs, then we have a responsibility-a moral imperative-and we're prepared to do what must be done."