??Even young boys on the rocky street outside know that it's not just good Samaritanism that brought 1,500 U.S. troops to this tiny country on the Horn of Africa. "Osama! Osama! Osama bin Laden!" the smiling kids taunt as the troops come and go quickly under the oppressive sun.

The war on terrorism has lured America back to the Horn of Africa. Not since the ill-fated effort against hostile warlords in Somalia 10 years ago has the United States established a base in this region.

Now Djibouti, a poor Muslim state few Americans have heard of or can pronounce (it's ji-BOO-tee) is the door to a vast and often hostile seven-nation territory that U.S. officials say harbors terrorists who fled Afghanistan and incubates new threats against the West.

The U.S. troops, including a contingent of secretive Special Operations Forces, now operate out of Djibouti. More forces, usually including 2,000 Marines, hover offshore. It takes seven words for Brig. Gen. Mastin Robeson, their commanding officer, to explain the reason. "We're here because the terrorists are here," says the Marine.

No one seems sure if Osama bin Laden himself is in the neighborhood, though he has been in the past. But dozens and perhaps hundreds of other members of bin Laden's al-Qaeda network and other terrorist groups are believed to be finding haven in the Horn of Africa and Yemen ? also in Robeson's purview ? where they are training and planning new attacks.

Security concerns are so high that plans for President Bush to visit the new U.S. Embassy in Kenya during his trip to Africa next month were scrubbed. The Pentagon on Friday warned U.S. interests in Kenya of a terror threat, citing new reports of al-Qaeda plans to launch an attack. The warning prompted the State Department to close the embassy for five days. It reopened on Wednesday.

To detect terrorists in this region and eventually hunt them down, the abandoned French Foreign Legion post known as Camp Lemonier has been transformed into a modern, air-conditioned base bristling with antennae.

Robeson, who has at his fingertips intelligence from satellite and radio communications, is watching a lot more than just a tiny republic on Africa's northeast coast. Within his jurisdiction:

? Yemen, across the Gulf of Aden to the north, is where bin Laden's father lived and where the USS Cole was bombed three years ago, killing 17 sailors.

? Somalia, to the southeast, is as lawless now as it was in 1993 when tribal militia battled and killed American soldiers who tried to control the unruly clans ? a clash made famous by the book and movie Black Hawk Down.

? Kenya, the former British colony, is where the U.S. Embassy was bombed by al-Qaeda in 1998. Last November, at the Kenyan resort of Mombasa, terrorists launched two simultaneous attacks. A missile was fired at an Israeli jetliner and narrowly missed, but a car bomb killed 14 people in the lobby of an Israeli-owned tourist hotel.

? Sudan, to the west, is where bin Laden lived in the mid-1990s before moving his headquarters to Afghanistan. It's also where, along with Afghanistan, President Clinton ordered a missile strike in retaliation for the 1998 embassy bombings in Kenya and Tanzania.

? Neighboring Ethiopia and Eritrea, best known for famine and tribal warfare, present opportunities for terrorists to blend in with the chaos. Like the rest of the region, their borders are porous and allow easy transit for terrorists and weapons.

These nations cover an area of 2 million square miles, more than half the size of the USA. To have an impact, the military is approaching the problem here differently than it did in Afghanistan or Iraq. There's no Taliban or a Saddam Hussein with an army that can be defeated in a conventional battle. There is no Northern Alliance or similar opposition group that's an effective ally. Instead, there are government and regional chiefs who have so many other problems that dealing with terrorism is a low priority.

Repairing neglected ties

So the U.S. military and State Department are repairing long-neglected ties to the governments and offering foreign aid, military assistance and other incentives to win their friendship and cooperation. Bush on Thursday announced $100 million in new U.S. aid to combat terrorism at African airports and seaports. The government of Djibouti already was set to receive $30 million this year ? making it one of the world's biggest per-capita recipients of American largess. The sum is nearly three times more than Yemen, a country of nearly 18 million where there is a significant terrorist threat, received in 2002.

Quietly, American spy agencies and uniformed forces have been working to create the intelligence network needed to identify terrorism before it strikes.

The United States was satisfied with minimal ties to the Horn of Africa until Sept. 11, 2001. Before that, the main interest was humanitarian. The region has few critical resources, little oil and a poorly educated population. Civil wars, including the ongoing turf fights in Somalia, made it a dangerous place for Americans to operate, as underscored by the 1998 embassy bombings.

It was only after terrorists, possibly including bin Laden, escaped the dragnet in Afghanistan that the United States became intensely interested in Yemen and northeast Africa. The Djibouti task force began life offshore on the command ship USS Mount Whitney last September. The task force command came ashore in May.

Djibouti was chosen as a land base because of its relative stability, security and central location. About the same size as Massachusetts, it is the smallest nation in the region in area and population. Most of its 600,000 residents live in the capital, also called Djibouti. Much of the country is an uninhabitable, volcanic desert where daytime temperatures of 115 degrees are normal. There is virtually no arable land.

The 1990s saw ethnic violence between Djibouti's two main ethnic groups, the Somalis and Ethiopians. But the last few years have been stable. Djibouti lacks the strong anti-Western bias of other Muslim states nearby.

The country and its most important economic resources, including a deepwater port, are still protected by several thousand French troops and Mirage jets a quarter century after independence. French soldiers frequent the bars and restaurants of the capital.

Germany, meanwhile, leads a flotilla of ships just offshore. They monitor shipping between the Indian Ocean and the Suez Canal.

Whatever the disagreements they had over the war in Iraq, France and Germany have cooperated with the United States here, where the Europeans have stronger interests and long-term ties. "This is not a U.S. operation. This is a coalition," Robeson says. "The transnational terrorist issue has the potential to sort of rise above local and even historical politics."

'That's why we're here'

Army Sgt. Jim Lewis's sunburned skin is oozing sweat and streaked with black grease. He's just glided 90 feet down a rope suspended from a Marine Corps CH-53E helicopter onto a dried riverbed near the Red Sea. It's the kind of skill the soldiers are keeping sharp should they need to raid a terrorist camp.

The objective this day, though, is just an abandoned beach camp a half mile away. Lewis and several dozen other members of the Army's 10th Mountain Division are practicing urban assault tactics, just one of the skills they might need in the months ahead.

A year ago, the division, including some of the 150 troops here, was looking for remnants of the ousted Taliban regime in Afghanistan. "If I was a terrorist, I'd be going to places like Africa. Djibouti. Finding a place to hide," Lewis says. "That's why we're here. To seek them out, be a show of force. Do whatever we can to find them and kill them."

Lt. Col. Lawrence Miccolis, commander of Marine heavy helicopter squadron 461and a Desert Storm veteran, says the mission in Djibouti is low-key compared to what's going on in Iraq. But in terms of fighting terrorism, it's critical. "There's probably not many things more important right now," he says after flying the Army troops to their training site.

Anti-terrorist missions are ongoing, but are not discussed publicly except in vague terms. Small teams are working with local commanders in Yemen, Kenya, Ethiopia and elsewhere. Sudan welcomed a U.S. military plane this spring for the first time in a decade.

Robeson won't say whether direct action, a euphemism for an armed attack, has taken place under the task force. The only well-publicized strike against terrorists in the region occurred in rural Yemen last fall. A Predator drone aircraft, reportedly operated by the CIA, fired a missile at a car and killed an alleged al-Qaeda kingpin.

With such a small force, Robeson says long-term security depends on convincing leaders and citizens that hosting terrorism is a mistake, especially ruinous to their economies. "We're here to empower them to take charge of their own destiny, to create that safe and secure environment."

A visit to Camp Lemonier erases any doubt that the United States intends to stay for a while. The Pentagon takes pains to call the U.S. presence in Djibouti temporary. The scene behind berms built to block prying eyes or truck bombers suggests a longer stay.

Thick new power lines lie in fresh trenches. Construction workers pour smooth concrete foundations for the expanding rows of air-conditioned offices. More than 700 local citizens build or do laundry or cleaning, making the base one of the largest employers in a country with an unemployment rate of around 60%.

"We see this as a mission that's more than just a handful of months," Robeson says diplomatically. "I think we see this as somewhere measured in a small number of years. I don't think we see this as a long-term mission."

Ibrahim Darar, chief of staff for the city's 5th District, says Djiboutians were skeptical of the U.S. presence at first. But now, he says, "they realize it's a good thing" to have the U.S. military around.

"We don't have any kind of real bad guy who is going to put in a bomb," he says, adding, the Americans "can stay as long as they don't interfere with our religion."

Work such as the digging of new water wells and providing medicines to the clinics wins friends here, he says.

The Hayabley clinic, an austere cluster of buildings, normally sees 100 patients in a day. In the past, many couldn't be helped because the clinic lacked medicine, especially antibiotics. Director Osman Muhammed says that with the Americans' help, more than 300 will be treated this day. "It's very beneficial for the people," he says. "It's a very good idea."

Robeson agrees. "It's got to be more than just coming here and saying, 'OK, how do we find bad guys and either capture them or kill them?' "