When a mystery illness swept through the African Union peacekeeping mission here, killing six soldiers and sickening dozens, doctors were stumped.
With help from the U.S. Centers for Disease Control and Prevention, they ruled out swine flu, tropical infection, rat-borne bacteria and even deliberate poisoning, as claimed by Somalia's insurgents.
But the culprit, doctors fear, is just as alarming: beriberi, a vitamin-deficiency disorder typically seen only in famines. Simply put, African Union soldiers appear to have died from a form of malnutrition.
It's the starkest example yet of how the mission in Somalia, which is authorized by the United Nations and largely funded by Washington, has become one of the most dangerous, yet least supported, peacekeeping operations in the world.
More than two years after the AU launched its effort to try to turn around this Horn of Africa nation, only 5,000 of the pledged 8,000 troops are on the ground, nearly all from Uganda and Burundi. Experts say even the full 8,000 would be half of what's really needed.
Though the new commander says he is intent on taking a tougher stance against insurgents who have growing ties to Al Qaeda, his force covers only about 8 square miles -- roughly one-third of Mogadishu, an area that includes the capital's airport, seaport and a cluster of buildings around the presidential palace that are occupied by the weak, internationally backed government.
The mission's projected $800-million-a-year budget has never been fully funded, with the U.S. contributing about $200 million this year. Funding shortfalls have forced commanders to depend also on donations, such as the new hospital building paid for by Britain and food rations from the U.N.
U.N. missions in the Democratic Republic of Congo and the western Sudanese region of Darfur each have four times as many troops, even though Somalia is the only operation in Africa where peacekeepers are routinely targeted by insurgents with mortars, roadside bombs and suicide attackers. Also, unlike other missions, there is no cease-fire agreement or U.N.-brokered treaty to enforce.
"How do you do a peacekeeping mission in a place that has no peace?" asked Maj. Anthony Lukwago, an AU commander from Uganda.
At a hillside AU outpost along Mogadishu's craggy coastline, soldiers have learned to improvise. They aim their 120-millimeter mortars using three sticks in the dirt, capped with upturned old cigarette packs marking the direction of insurgent strongholds miles away. Only recently did soldiers receive upgraded flak jackets and armored personnel carriers capable of withstanding the kind of roadside bombs they face.
On the campus of Mogadishu University, now serving as headquarters for Burundi's contingent, soldiers face roadside bombs virtually every time they leave the base. Nevertheless, they can't get basic bomb-detection devices to sweep the streets or equipment to defuse the bombs.
Their solution? Drive fast and travel at irregular hours, according to Brig. Gen. Prime Niyongabo, commander of the Burundian contingent.
"There is so much we need," he said.
Erin Weir, a peacekeeping advocate with Refugees International, credited the AU presence with preventing Somalia's transitional government from being chased out of the country altogether, but added that the worsening security situation has altered the character of the mission. "What they are doing is not peacekeeping," she said. "It's more a military task."
It's little surprise that the mission has become one of the deadliest in Africa. Thirty-three AU soldiers have been killed, mostly by roadside bombs. Eleven of these troops died in a suicide truck attack this year. An additional 20 have succumbed to malaria and other diseases, AU officials said, including last month's suspected beriberi outbreak
Most of those sickened were recovering thanks to vitamin B1 injections, according to AU doctor James Kiyengo. That treatment was followed by preventive thiamine supplements for all soldiers and a reexamination of meal plans. Soldiers complain that the mission supplies them with meat just two or three times a week, no eggs and only rarely fresh vegetables. Commanders said they hadn't come to a conclusion as to what caused the illness.
The peacekeeping mission has also grappled with a vague, ill-fitting mandate that tightly restricts troops' ability to combat insurgents, who scarcely existed when the mission started. The mandate calls for the AU to protect the government and its institutions. Safeguarding Somalia's beleaguered civilians, half of whom survive on international aid, is not part of its responsibility.
As a result, the mission, known as AMISOM, is frequently dismissed as weak and ineffective. "If they are going to hide behind their sandbags while people are suffering, they should go back home and enjoy a glass of wine," said Mahdi Ibrahim, 23, a frustrated Mogadishu resident.
AU officials have attempted to court public opinion by sharing their water supply with neighbors and opening their clinics to the public.
But officials said the mission's mandate mainly permits self-defense. Insurgents "could have a party in front of our gate and we couldn't do anything unless they attacked us first," said Maj. Barigye Ba-Hoku, the mission's spokesman.
Speaking at AU headquarters inside a whitewashed, bombed-out mansion overlooking the Indian Ocean, Ba-Hoku said insurgents use the AU's mandate and rules of engagement against it. For instance, he said, they often fire mortar shells from residential neighborhoods because they know AU troops won't fire back at civilian areas.
He said that once a busload of insurgents disguised as civilians approached an AU base, singing as if members of a wedding party. As they left the vehicle, they drew guns and attacked.
Soldiers say they've grown tired of being on the defensive -- and of the criticism that comes with it. Many are itching for a fight.
"We could overrun Mogadishu in no time at all," Lukwago said, noting that the AU force is the only one in Somalia with tanks, Katyusha rockets and long-range mortars. The troops' foes, he added, "are not military guys."
"They are a bunch of boys. They are not trained."
Until recently, AU political leaders and the U.N. resisted requests by AU military commanders that their troops be allowed to go on the offensive, fearing such a move would only escalate the violence and allow insurgents to taint the soldiers as "foreign invaders."
But the newly arrived force commander, Ugandan Maj. Gen. Nathan Mugisha, said he had received a green light to get tougher. "We can preempt," he said. "We don't have to be like sitting ducks, waiting to be beaten like a drum."
In an instance of the new approach, AU troops last month responded to an insurgent attack on the presidential palace by engaging for the first time in a sustained street battle, pushing the insurgents back more than four miles. It was the farthest AU troops had fought beyond their zone.
Two weeks ago, in a show of force, an AU convoy patrolled through an insurgent stronghold, drawing fire. No one was hurt.
Somalia's president, Sheik Sharif Sheik Ahmed, is encouraging the AU to jump into the fight, saying operations against insurgents are justified under the mission's mandate to support the government.
"Mogadishu is the seat of the government and it should be free of insurgents," Ahmed said in an interview at Villa Somalia, the heavily guarded presidential palace. "There are many different forms of self-defense. Preemptive defensive action can be taken."
Ahmed said the AU's positions in the capital have allowed his army, which is really a collection of allied militias, to take its battle to different parts of the country. In recent weeks, government forces have made headway near the Ethiopian border.
But analysts worry that unless more international support is forthcoming, the AU force will become overstretched. Michael Weinstein, a Purdue University political science professor, blamed Somalia's limbo on the international community's hesitance.
"The West has been reluctant to go full throttle, and they've ended up with a wishy-washy policy," he said. "Meanwhile, AMISOM is stranded. They're stuck in a box."