Michael von der Schulenburg drove deliberately into the riot. Angry men filled a main road here in Freetown; they quickly surrounded his car. They were members of the APC, the All People's Congress, and their leader, Ernest Koroma, was Sierra Leone's president. They were in a dispute with their opposition over a local election that had taken place a day's drive deep into the countryside.

That rural dispute turned national and urban, and threatened to turn violent in Freetown. Thousands of APC men thronged toward the headquarters of the opposition party. They were drunk, and they were being used. Men here are cheap – a beer buys a vote – but they are not usually violent.

Mr. Schulenburg, the United Nation's top man in Sierra Leone, hadn't been in the country for long, but he did know this: So many men don't gather by accident, nor do they spontaneously decide to fight over such a paltry political event as a rural vote. Schulenburg didn't know who had reported the crowd, or why. He's friendly with Sierra Leone's "Big Men" – he chats daily with Mr. Koroma by phone. But that day, no one would take his calls.

As he approached the action, he wondered: Was this the kind of raucous discontent typical of Sierra Leonean politics, or was the street rumor right? Could it be the moment that the war comes back?

He focused again on the building, where 22 men cowered on the roof. Below them, the crowd shouted, "Hand them over! Hand them over!"

When Schulenburg retells this story, he pauses here. He doesn't want to sound like a hero. Not because his presence didn't calm things – it did – but because casting him as a hero misses the point. For him, the drama is in the diplomacy.

"We had so much credibility, they let us go through," he says of the crowd. "We reorganized the police; we negotiated so that people could come off the roof. And afterwards, we negotiated a sort of peace deal between the two parties."

And Schulenburg did this all remarkably quickly. The men were moved off the roof in a matter of hours, and discussions held over a matter of days. Only two weeks after the 2009 standoff that observers feared would mark Sierra Leone's return to war, its two major parties announced a new agreement that became the foundation for political fair play.

If Schulenburg hadn't driven into that crowd, chances are high that the 22 men would have been murdered by the mob below – even that the violence may have escalated. "I can do that because I have a political mandate," he says. That's UN-speak for saying that Schulenburg has a form of permission no one else has – not ambassadors, not World Bank officials, not aid workers with the deepest of pockets: He has "peacebuilding."

•••

Peacebuilding is a new approach to ending war, and it's becoming a global buzzword. It's different from peacemaking, which brings politicians around a table to hammer out a peace deal. And it's different from peacekeeping, which sends foreign soldiers to monitor peace agreements, separate warring parties, and protect civilians in conflict zones.

"Everybody understands peacemaking," says Judy Cheng-Hopkins, the UN assistant secretary-general for peacebuilding. "And in a way we also understanding peacekeeping.... Peacebuilding goes beyond either [of these]."

Peacebuilding is about what comes next – the slow and thankless slog of building a country back up. For generations, that job has been piecemeal: a little emergency aid here, some development projects there. But those professionals are trained differently, rarely coordinate, and are sometimes outright antagonistic. Their projects, meanwhile, are not overtly about peace. Aid is about relief; development is about economic growth. But post-conflict states also have a host of other needs.

Ex-soldiers need to feel productive and engaged as civilians, or they cause trouble. Returning refugees need a legal process for lodging complaints when they find their old homesteads occupied. Courts need competent judges and lawyers; armies need barracks; police need jail cells. Often, these countries need all these things, and all at once.

None of these needs is especially surprising. "There is this sense that everyone knows what we're talking about. We're talking about a specific set of challenges in a specific set of circumstances," says Vanessa Wyeth, coeditor of "Building States to Build Peace." "They're based on a lot of experience but not a lot of specific evidence about things that we know can help support peace."

The UN Peacebuilding Commission (PBC) is setting out to build that evidence. With $155 million so far, the UN's newest office is testing theories about war, peace, and development in six African countries – Guinea, Guinea-Bissau, Liberia, and Sierra Leone, in West Africa, and Burundi and the Central African Republic (CAR) in central Africa.

"Usually people say, 'We have so many UN bodies, we have so many UN agencies in different countries – one more? What for?' " says Jorge Tagle, a counselor with the Chilean mission to the UN, which formerly chaired the PBC. But he and others think its design and membership mean this little commission could have big influence – over major UN decisions, and in the countries with which it works. [Editor's note: The original version incorrectly identified the nationality of the mission Mr. Tagle represented.]

That's because the PBC is something other organizations aren't allowed to be: overtly political. Schulenburg's negotiations in the midst of the Freetown riot were not just a bit of practiced conflict resolution. It is, he acknowledges, an "interference in national sovereignty."

The PBC gets that leeway because it's part of the UN, and because it's invited. Countries must ask for PBC help. In return, they get a dedicated, if unofficial, ambassador for their cause. So far, the arrangements have paired neglected countries like the CAR with power-hitters like Belgium, who advocate for their partner countries at donor round­tables and in political meetings for funding, attention, and that elusive, powerful ingredient of action – political will. In the CAR's case, donor money to the country increased more than 50 percent the year it joined the PBC.

In its first five years, the PBC has succeeded most where it exploits its permission to be so political and interfere so heavily.

In Burundi, the commission's support helped to decrease the reported use of torture by intelligence forces friendly to the president by as much as 80 percent, says a local human rights group. In the CAR, it helped push forward a political dialogue that brought an end to an ugly rebellion.

From refugee return to building army barracks to elections, "all of it is very, very political, and for that you need a political body," says Ms. Wyeth. "You have a lot of different international actors playing a lot of different roles in these countries, and you need some political mechanism to bring all these actors together, to hold them more accountable, and to have more transparency about what the international community is doing in a country."

So far, the commission works only in Africa. Technically, that's because only African countries have so far asked to be PBC partners – which in turn may influence which countries ask for help. "There's a kind of stigmatization, but I think it's ill-placed," says Ms. Cheng-Hopkins. "This is not a poverty commission.... Unfortunately ... it happens that, so far, a lot of the [countries] that come on belong to the very poorest in the world."

Still, as a word, 'peacebuilding' sounds weak, It's an awkward compound noun – an aspiration, composed – as if shoving into a single word two pretty good ideas clears the way toward achieving them. "If you ask me to show you the thing called peacebuilding, I can't," says Peter Ngu Tayong, a media adviser in the UN's Sierra Leone headquarters. "Nobody has seen the animal called peacebuilding."

The PBC's funding arm, with money from 47 UN states, supports 173 projects in 19 countries. But they, alone, are not a measure of peacebuilding. In a world glutted with aid projects, it's easy to miss what may be the revolutionary part of peacebuilding: It demands attention to process.

For most of modern history, peace was a matter of paper. Politicians sat around a table, hammered out a cease-fire, and signed it. Peace was a matter of what powerful men decided in consultation with one another, not a condition to be rebuilt and sustained for a broader community.

That neglect often turns into state failure. Paul Collier, author of "Wars, Guns and Votes," writes that 40 percent of postconflict countries slip back into violence within a decade – and that those relapses make up 50 percent of the world's civil wars. Examples of reversions to violence are plentiful – Rwanda and Burundi; Liberia and Côte d'Ivoire; Uganda and Sudan – but they aren't confined to Africa. The condition holds in Indonesia, Georgia, the Philippines, Colombia, Lebanon, and Haiti.

As the United Nations examined its own failures in the 1990s – especially the peacekeeping debacles in Rwanda and in Bosnia, where hundreds of thousands of civilians were slaughtered as the UN stood by – its leaders brainstormed a new approach to peace. "Our record of success in mediating and implementing peace agreements is sadly blemished by some devastating failures," acknowledged Kofi Annan, then secretary-general of the United Nations, in a 2005 speech that first proposed the PBC. "Indeed, several of the most violent and tragic episodes of the 1990s occurred after the negotiation of peace agreements."

Peacebuilding happens outside the halls of power – in the fields, where men who once fought now farm; in schools where child soldiers learn trades; in courtrooms and parliamentary chambers, where problems once solved with weapons are submitted to tedious democratic resolution.

These are not usually the priorities of politicians divvying up the spoils of war. Yet work by Collier and others suggests that these are precisely the processes that can help prevent the next war.

That possibility is acutely felt in places like Guinea-Bissau. The small West African coastal nation is known, if at all, as a narcotrafficking hub between South America and Europe, or as home to frequent, bloody coups.

Ordinary Bissau-Guineans articulate the same thing that social scientists do. From 2008 to 2009, the grass-roots community organization Voz di Paz ("Voice of Peace") undertook a survey, asking people to list what they thought causes violence. "Bad governance" topped the list, followed by poverty.

When a new peace doesn't stick, the rest of the world pays the price. UN peacekeeping missions cost $8 billion in 2010; the United States paid 27 percent of that bill. Peacebuilding costs pennies in comparison. "If Sierra Leone had ended peacekeeping just six months earlier, the savings would have paid for 20 years of peacebuilding," says Schulenburg.

Talking to peacebuilders can leave the impression that the PBC revolution is really about easing UN bureaucracy. But in the countries where it works, it's more than that. Some say this new idea is the best barometer of whether the massive, often unwieldy, good intention that is the UN works at all. "The UN's relevance ... is what we do on the ground," says Schulenburg. "That's our litmus test. There's nothing else.... It's: Do we get it right here?"

•••

Freetown's Siaka Stevens Street throbs with people, even when it rains. Pedestrians vie for precious sidewalk space with vendors and their goods. Men sell shoes and pirated mix CDs; women offer peanuts and panyas, long strips of colorful African fabric. On a busy corner, a man sells coconuts out of a wheelbarrow. Informal commerce is everywhere.Not far from the coconut vendor, near a favorite expatriate lunch spot, is commerce of the formal kind: bustling banks. Inside one, Joseph Sam and Tejan Sesay, two tellers, sit beside fat turquoise bricks of leones, the local currency. Clients wait patiently as the counting machine slurps up a stack and spits them back out; then they stash colorful stacks of cash in paper bags and walk out.

Mr. Sam wears a black suit; Mr. Sesay wears a button-down shirt with an embroidered collar and cuffs, and both young men wear cufflinks – a subtle show of disposable income. They would have been children during Sierra Leone's decade-long civil war, not much older than the child soldiers infamously impressed into militias and drugged into committing horrible crimes.

They have never heard of the UN Peacebuilding Commission – nor have many ordinary citizens in any of the PBC's partner countries. But for Sam, the idea inspires fatigue: "Nobody needs to tell me not to go to the bush and take up arms. We are here at 7 in the morning and we leave at 7 at night. It takes an hour to get to and from home. We don't have time for fighting." Sesay nods: "It's the idle mind that thinks a lot of silly things."

"We already have peace," Sam adds. "What we need is investment.... So-called donors need to push money into industry."

Freetown buzzes with this new feeling of being over it all. Even several hours from the capital city, in a town called Makeni, there's an impatience with the image of a war-haunted nation. "Obviously, the country is over the war. Obviously," says Alfa Kamara. He rattles off signs of progress: A paved road connects locals to the capital in just two hours, a trip that used to take most of a day. Tractors have begun to appear in the fields. Hospital visits are free for kids younger than 5.

But Kamara, an experienced mason and the father of two young children, can't find a steady job – or, at the moment, any work at all. Most of his friends are in the same position, he says. So he sits outside a small shop, near the pavement, and plays the lottery with friends. He comes here every day, trying his luck with small sums. (He's won only once, he says, the equivalent of about $15, or about 10 days of work.)

"We are very angry. Very angry," Kamara concedes. "But we are not going to take up weapons again."

That's because he feels heard; Kamara says radio call-in shows give him and his friends a chance to air their grievances and sometimes to talk directly to a politician. That communication was missing before the war, which made people resentful, he says.

Kamara's words are a peacebuilder's solace. Local government officials and international observers agree that a key cause of the war was the feeling by frustrated, unemployed young men that rebellion was their only option. Indeed, the PBC's financial arm has invested $4.1 million in youth employment and "empowerment" programs in Sierra Leone, hoping that targeting a cause of the past war will prevent future fighting.

•••

Getting the theory right is only part of the job. It's common postconflict wisdom that swollen armies need to be reduced, and ex-fighters from all sides reintegrated into civilian lives. But in Burundi, where ethnic conflict and civil war have ravaged the country since independence in 1962, the demobilization of ex-soldiers has been problematic. The PBC began working here in 2007; the last rebel group signed a peace deal in 2009. Yet the reintegration – of ex-rebels and redundant soldiers alike – has been delayed by interminable national politics. So in Gitega, a provincial hub two hours north of the capital city of Bujumbura, no one is counting on a promise like Kamara's.

"There were lots of promises for ex-soldiers from different institutions," says Jean-Marie Nindorera, who leads an association of nearly 150 ex-combatants near Gitega. "When they didn't come true ... [ex-combatants] were not satisfied."

"I can see they're just waiting, waiting. They're very angry," says Oscar Ndiswarugira, who works with ex-combatants on behalf of the Ministry for Peace and Reconciliation Under the Cross (MIPAREC), a grassroots organization. "Some of them are very powerful.... The issue is how long they are going to be patient."

•••

If peace deals themselves may not be enough to make peace, it's also not always enough, after war, to tackle institutions and infrastructure. Where the PBC has tried to play it safe, it hasn't worked: Despite $3 million in political dialogue workshops that got rave reviews from external evaluators, actual political dialogue in Burundi – between the workshop participants – came to a halt during national election disputes last spring.

Burundi's electoral experience does raise the question: Is peacebuilding working? Some of the new UN programs are clear successes, like the reduction of torture in Burundi. Others have been hampered by the usual spoilers – inertia and corruption. In the CAR, for example, the demobilizing of ex-combatants was delayed for more than six months, and a government minister in charge of overseeing the project absconded with half a million dollars, according to local UN workers. Several UN staff in peacebuilding field missions say the blank-check model of the commission's funding arm, the Peacebuilding Fund, posed problems on the ground. The fund positions itself as a flexible funder interested in "quick impact" projects.

"Money was suddenly on the table with nothing around it, and everybody tried to grab something from it. That was a fundamental mistake," says one Sierra Leonean staffer.

And another Sierra Leonean staffer, who also didn't want to be named, warned that a preoccupation with funding peacebuilding projects risks distracting the commission from the processes it uniquely can influence: "My own sense is that the PBC needs to help with dealing with real fundamental issues. You can't see them, you can't touch them, but you know they're there ... and those are the last things to change."

Still other countries seem like odd cases for peacebuilding. "Guinea-Bissau was maybe, in a way, the wrong evaluation of the PBC," says Frank Jarasch, at the time an adviser to peacebuilding chair Peter Wittig, the German ambassador to the UN. After a 2008 coup and an ongoing stalemate between the civilian government and the military, he says, "it's certainly going to be difficult to get back to a stage where peacebuilding might be concrete and successful."

Even so, Mr. Jarasch thinks any international engagement in such fragile situations is worthwhile. Others concur, because the PBC shows a troubled and troublesome government that someone is watching.

"I certainly think you have a lot more attention paid to [PBC member countries], and much more sustained attention, than you had had," says Wyeth. At the same time, she says, "you've certainly seen governments held to higher levels of scrutiny by the PBC in New York."

Still, it may be too early to tell.

"Nation-building in all of our countries has been an extremely long, bloody affair.... This is a country which still tries to create a nation that people feel like they belong to, together," says Schulenburg. "They're trying to bring democracy, and to do it peacefully. That's not been done in history. So let's not be arrogant about the whole thing. Let's see how we can help to speed it up."

•Travel for this article was funded by a grant from the Pulitzer Center on Crisis Reporting.