

Displaced civilians take shelter at the United Nations mission in South Sudan. (Tony Karumba/AFP/Getty Images)

It was considered one of the world's great successes when, on July 9, 2011, South Sudan became an independent nation. After many unhappy years as a region of Sudan, the new country declared its independence with crucial support from the outside world, particularly the United States.

Now, less than two and a half years later, South Sudan appears to be on the verge of a potential civil war. Since an alleged coup attempt Dec. 15 (it probably wasn't really a coup), fighting between rebels and government forces has killed at least 500, injured four U.S. troops and left entire cities disputed. As of this writing, the South Sudan army says it's preparing to attack rebel groups who've taken control of oil-producing regions. How did this happen?

The roots of South Sudan's conflict extend back much further than the country's 2011 independence. And, while all internal conflicts are complicated, this one is especially so. But you might say that, in the most general terms, there are three big forces driving the conflict: (1) South Sudan is very poor and underdeveloped, and resource scarcity tends to fracture politics and exacerbate ethnic conflict; (2) The same forces that helped South Sudan win independence -- militias, strongly felt tribal identities -- also set it up for today's conflict; (3) More narrowly, the country's president had fired the vice president, starting a political dispute that may have been the match to South Sudan's tinderbox.

Let's go through those one by one.

1. South Sudan's poverty exacerbates its ethnic divides.

To be clear, it's not that being poor in itself makes a country prone to conflict: the problem is when resources are scarce and there isn't a good system for distributing them. That forces people to compete for resources. And that competition can cause social divides to widen. In South Sudan's case, the divides are ethnic. Or rather, they began as ethnic and have since become political.

South Sudan is especially susceptible to this problem because its economy is a very unlucky mix of poor people, a poor state and rich resources. South Sudan's GDP per capita is about $1,000, one of the lowest in the world. Its infrastructure is practically nonexistent, with only a few dozen miles of paved road across a nation the size of Texas. But the country has an awful lot of oil. That means that South Sudan is poor in ways that make people more likely to compete for resources, because individuals don't have very much, but the country is also rich in ways that make people more likely to compete, in this case for control over the oil.

This has created some very fertile economic conditions for internal conflict. But it gets worse.

2. The country's path to independence was also a path to internal conflict.

The decades before South Sudan's independence are complicated but, in the simplest terms, it was defined by a half-century of fighting between the politically dominant, ethnically Arab north and the politically weaker, ethnically sub-Saharan south. Rebel groups in the south wanted more autonomy from the north. They had to fight very hard to get it (although they owe a lot to the north, which behaved so terribly that it galvanized world opinion in favor of the south).

The thing, though, is that South Sudan is actually pretty ethnically diverse. South Sudan, like a number of other countries in sub-Saharan Africa and particularly this region of it, is articulated by borders that have very little to do with the actual people there. The earlier, unified version of Sudan had been carved out, in part, by European and especially British colonialism. The long-running conflict between the country's north and its south was, like many wars in post-colonial Africa, partly a consequence of European cartographers having forced disparate groups into artificial borders. Splitting Sudan in two helped to ease the tension created by these borders but didn't solve it. The southern ethnic groups had been united by a common enemy -- the north -- but that's no longer bringing them together.

People in South Sudan don't identify that strongly with their nationality: the idea of South Sudan is too new for most people to have internalized it as their national identity, and the old unified Sudan was too hated and in any case too artificial. So people have defaulted to an ethnic or tribal identity. That's fine; people can identify however they want. But because of all that resource competition, it makes it that much tougher for everyone to come together for "South Sudan" if they care a lot more about their fellow Dinka or Nuer. (To be clear, that doesn't mean the ethnic groups are internally unified -- they're not -- but people still tend to group ethnically.)

The country's demographic composition is just about right for people to divide violently along ethnic lines. The largest group, the Dinka, makes up only about 15 percent of the population. The next-largest, the Nuer, is about 10 percent. There are dozens of other ethnic groups that speak dozens of languages.

As Stephen Saideman, a political scientist who studies ethnic conflict, wrote this year: "In societies that have very little diversity, there is no opportunity for [ethnic] violence. For societies where there is a great deal, there is no threat of dominance. But in places where there are a few groups that rival each other, then the threats they pose to each other or at least one to the others can be severe. Ethnic violence may not be about fractionalization/diversity but about polarization."

So, in South Sudan, you previously had lots of ethnic groups organizing along ethnic lines so that they could come together (if imperfectly and inconsistently) to fight the north. Now they've lost that unifying enemy but still have the ethnic organization, and are being pushed toward competition by the economic conditions we talked about earlier. Worse, South Sudan's history of the last few decades has been one where the state doesn't have a monopoly on violence; militias have had a lot of that power. So it's much easier for people to resort to militias as a sort of default, making it much more likely for political or ethnic disputes to turn violent.

3. A political rivalry that became ethnic.

This is where we get into this week's conflict. The president since independence, Salva Kiir, is ethnic Dinka. His now-former vice president, Riek Machar, is Nuer. But Kiir saw Machar as a rival -- probably with some reason -- and fired him in July. You can probably guess where things went from there.

If this were, say, Iceland, then a contentious and controversial rivalry between the nation's two leading politicians would probably be seen as mostly just political infighting, or at most perhaps a clashing of political parties or ideologies. But Kiir and Machar are the two most powerful people from their ethnic groups in a country where ethnic grouping is very important. So a fight between those two men was bound to exacerbate tension between their respective ethnic groups, which also have lots of other people in positions of power.

On Dec. 15, some soldiers loyal to Kiir clashed with soldiers loyal to Machar. (Think back to the part above, about ethnic fractionalization; South Sudan is one of many countries where people are expected to feel loyal to their country as well as their tribe or ethnicity, something that can obviously cause conflict.) Kiir accused Machar of trying to stage a coup, although that's probably not what happened. Since then, fighting between the respective groups has spread, with forces loyal to Machar now having seized small but significant pieces of territory.

Eric Reeves, a Smith College political scientist who studies South Sudan, told my colleague Sudarsan Raghavan that, given the ethnic diversity within the army, “the events of the last days were, if not inevitable, all too likely.”

"If not inevitable, all too likely" is a good description for South Sudan's conflict. To be clear, there's nothing inherent to the people of South Sudan that makes them any more or less prone to conflict than people from any other countries. But there are certain economic, demographic and political factors that, in any country, make internal conflict more likely. A significant number of those factors are present in the world's youngest country, and to a dangerously high degree. South Sudan is just unlucky.