Vigilant Yemeni snipers in light-green camouflage and polished black army boots carrying machineguns block the gates to the US Embassy.
The massive concrete and iron diplomatic compound is officially closed for a US government "security review." But inside, there's a bustle of activity. Members of a US Marine contingent lift weights and jump rope to stay fit; others oil and shine their M-16s. Green Berets and CIA operatives plot their next move.
Today this bunkered embassy is just one frontier outpost in a new phase of America's "war on terror."
From Afghanistan to former Soviet Georgia and the Philippines, US forces are training local armies to take on Islamic insurgencies. But recent successes - and failures - here in Yemen exemplify the challenges of collaborating in key terrorist hot spots around the world.
The fallout in Yemen following the Nov. 3 Hellfire missile strike, in which six Al Qaeda members were killed in a missile launched from a CIA-operated unmanned drone, is a case in point. The Yemeni government and US targets there have faced subsequent reprisal attacks.
The US contingent is trying to train backward local "special forces" to perform difficult "hit and snatch" operations against suspected Al Qaeda cells operating in the desert areas. On top of the military challenges are domestic and international political obstacles.
In this case, the local forces are led by the president's inexperienced son, and botched one attempt to capture the key Al Qaeda leader - Qaed Senyan al-Harithi - who was later killed in the US strike.
A larger challenge: The US has to be careful not to make the ruling regime look as if it's cooperating too much with America, because that could create domestic unrest that might topple the government.
Just a week ago, Yemeni officials publicly acknowledged that they had cooperated in the Nov. 3 Hellfire missile attack. There have also been reports - although Yemeni officials won't publicly comment - that the top Al Qaeda suspect arrested last Thursday, Abdul Rahim Al-Nashiri, was picked up at an airport in Yemen and quietly turned over to the US.
"Yemen has to contend with US pressure to eliminate the considerable Al Qaeda presence in its territory," says Bernard Haykel, a Yemen expert at New York University. "But it also has to deal with a population that is broadly sympathetic to Osama bin Laden's political aims."
This week, former Yemeni Prime Minister Abdelkerim al-Iriyani confirmed during a US visit that Al Qaeda members killed in the Hellfire missile attack were not only guilty of participating in the attack on the Cole, which killed 17 Americans, but also were planning "sabotage operations against oil and economically strategic facilities" in Yemen.
It is this kind of activity, where the terrorists turn on the host government, trying to drive a wedge between the people and the government, that has Yemen most worried. That, experts say, is what pushed Yemeni officials to cooperate more fully with the US last fall.
In August, two Al Qaeda members blew themselves up in an attempt to kill Yemeni officials. After that, Yemen agreed to allow US military and CIA teams in the country to train Yemen's special forces.
"Al Qaeda has clearly declared war on the Yemeni government, and on President Saleh himself," says Dr. Haykel. "It became very clear what the president had to do - he had to align himself with the US."
But, Haykel goes on to say, the result will likely lead to more terrorist attacks against the oil industry in Yemen, the country's main source of income.
"Al Qaeda has done this by attacking the French oil tanker [in October]," he says. "They will strike where it harms the most - at the shipping and oil industry."
Originally, about 100 US Special Forces soldiers were in Yemen. Now, about two dozen remain. In nearby Djibouti there are another 800 Special Forces, plus the CIA unit that operates the Predator drones used in the recent missile attack.
But training the Yemeni forces has not been easy. Although nearly every male above 13 years of age owns an AK47, Yemen isn't known for its military prowess. Ahmed Saleh, the special forces leader and son of President Saleh, has apparently been groomed by his father in the same vein as Saddam Hussein's sons.
Ahmed was first made a member of parliament, where he was ineffective, then sent to a military academy in Jordan, where he flunked out, according to a former US government official with broad experience in the region.
But Ahmed had met Jordan's King Abdullah and was impressed with his special forces' capabilities. When he returned home, the former US official says, Ahmed asked his father to give him his own special forces unit. His father gave him the unit but not money or equipment.
"Everybody called it the hollow brigade," says the former official.
After US troops spent some time and money training the Yemeni unit, they sent it on a mission to capture Mr. al-Harithi, who was being sheltered in the Marib region. But al-Harithi and his followers were able to ward off the Yemeni forces, and killed 18 of them in the process.
A Western diplomat says that happened because of the way the Yemeni special forces handled the operation - including the use of jet that broke the sound barrier over the village just as the operation began. Al-Harithi and his comrades got away.
So when the CIA and US Special Forces received intelligence on where al-Harithi was located earlier this month, they decided to do the job themselves, according to the Western diplomat.
But that incident - and the fact that the US publicized its success - has put Yemen's government and the two dozen or so US soldiers remaining in Yemen, at heightened risk of reprisals.
"The US rush to announce the Nov. 3 strike, apparently without informing the Yemen government in advance, was not well calculated," says Charles Dunbar, a professor of international relations at Simmons College in Boston and US Ambassador to Yemen during the Gulf War. "The economic situation in Yemen is grim, and it will not be hard for those opposed to the cooperation to inflame the sentiments of people whose pocketbooks are empty."
Yemen is bracing for more terrorist attacks. In fact, a senior Yemeni official's home was hit by a grenade last Tuesday, causing serious damage, but no deaths.
"I was very optimistic when the US first said they would help Yemen build its security forces and coast guard," says Yemeni Brig. Gen. Yahya al-Mutawakel. But "the result is not satisfactory. We have not yet made the Americans understand that they are here to help us fight for ourselves."