The African Union came to Tawila this weekend to investigate the kind of incident it had hoped would no longer happen under its watch.
For a week, tensions in this strategic town in North Darfur had boiled over, pitting ethnic Africans and Arabs against each other in mob violence. Then, just after dawn prayers last Monday, rebels attacked the town, killing nearly 30 government police officers and pocking the garrison with bullet holes. The government retaliated with airstrikes. People ran any way they could. Like so many other towns in Darfur, Tawila virtually emptied.
The African Union has struggled to make that familiar trajectory -- a rebel attack, a government airstrike, the flight of civilians, another ghost town -- a thing of the past in Darfur, the vast region of western Sudan ravaged by nearly 22 months of war.
Under heavy pressure, the government has allowed more than 3,000 African Union troops to enter. Although those troops are authorized only to monitor the country's tenuous ceasefire and not to intervene in fighting, their aim is to help prevent further violence just by being here.
But even that goal has proved elusive for a force hamstrung from the start by its small size, lack of expertise and most of all by its strict rules of engagement. The challenge it faces was perfectly summed up by the mission in Tawila this weekend.
On Sunday morning, a team of nine African Union military observers, trailed by the first journalists to visit this town since last week's attack, stared at the shallow crater that a government bomb had left in this now charred group of huts. One of those huts was no more than a circle of black ash, with an earthen water jug lying on its edge. A woman had lived here with her five children.
The African Union monitors snapped pictures of the bomb site. They interviewed local people who had stayed and many more who had come back because they had heard the African Union had come.
The team members, who are unarmed, had risked spending the night before in the frigid desert on the edge of town -- mainly, they said, to show people that they were there.
During the day, they handed out their uneaten military rations to women who straggled up the sand streets. By midafternoon on Sunday, they prepared to leave.
As they did, a group of men rushed up and said that they feared the police would harass those who had spoken to the monitors. The head of the team, Lieutenant Colonel Ahmed Fouad, of Egypt, listened and nodded. Later, when asked what he would do about the men's plea, he said he would write it in his report and pass it along to headquarters. Until there are enough of them to keep vigil on Tawila, he said, there was nothing more he could do.
And then they left -- headed back to their base in the state capital, El Fasher, in a long white ribbon of four-wheel-drive vehicles and armored personnel carriers.
For the African Union itself, a nascent organization representing African governments and struggling to shake off the mantle of its largely ineffectual predecessor, the Organization of African Unity, Darfur represents a crucial test. If the union's mission succeeds in Darfur, it will score a major credibility win. If it fails, the price will be dear.
"We will take a long time to recover our credibility toward our people and our partners," Jean-Baptiste Natama, an African Union senior political officer, said in an interview in El Fasher last week.