The world’s newest country is on the brink of civil war. On December 16, South Sudanese president Salva Kiir announced that former Vice President Riek Machar, whom he dismissed in July, had launched a failed coup attempt. Kiir wore military fatigues rather than his now-iconic cowboy hat, the original of which was a gift from then-president George W. Bush.

As Africa security analyst and CNA researcher Lesley Ann Warner has noted, it’s unclear whether Kiir was telling the truth about the coup attempt, but it’s significant that he kicked off his presser by harkening back to internal conflicts within the governing Sudanese People’s Liberation Movement in the early 1990s, when the SPLM was in the midst of a 20-year-long insurgency against the Khartoum government. Kiir, of the Dinka ethnic group, and Machar, from the Nuer, have been at this for a long time. Their grudge, and the ethnic cleavages it embodies, long predate South Sudan’s independence from Khartoum in July of 2011, and they now have the potential to plunge the country into even deeper chaos. Machar has fled the capital—Warner has started a #whereisRiek hashtag on Twitter—and the past few days have brought credible reports of heavy artillery fire and organized ethnic violence.

There was always evidence that Kiir’s control over the country was basically non-existent, and that the SPLM lacked either the expertise or the intention to reverse course. The past two years have been pock-marked with troubling hints of the country’s fragility, like the devastating attack on a UN convoy in April, and Kiir’s shocking announcement in June of 2012 that $4 billion had been lost to corruption during South Sudan’s first year of independence. An early warning sign was the Juba government’s expulsion of American advisor Ted Dagne, a former Congressional Research Service specialist and longtime proponent of South Sudanese independence, in August 2012. That the SPLM had so quickly turned on one of its most dedicated American allies suggested that corruption and factionalism were winning out in Juba, a suspicion that was all but confirmed by Kiir’s heavy-handed cabinet reshuffle this past July—a gambit that included Machar’s firing. There were subsequent crackdowns on the media, and ten senior politicians have been arrested amid this week’s violence.

The violence is neither inevitable, nor completely unforeseeable. Whatever its cause, it has dispensed with even the illusion of a stable center of authority, or the appearance of a semi-functioning sovereign state. Of course, even this veneer of order was thinner that it appeared: ethnic violence has plagued the northeastern state of Jonglei since independence. David Yau-Yau’s anti-Juba militia in Jonglei was allegedly supported by the still-hostile Khartoum government, and disagreements over the split of oil revenues with the north led to a government-mandated shutdown of  South Sudan’s oil industry and a long, crippling period of austerity. There were border skirmishes in April of 2012, which led to northern airstrikes on southern cities and nearly triggered an all-out war. There’s the ongoing anti-Khartoum insurgency in the Sudanese states of Blue Nile and Southern Kordofan, which many believe to be a proxy conflict between the northern and southern governments, still on something of a war footing toward one another. There was the total lack of infrastructure, the arrival of tens of thousands of southern returnees from the north, and a literacy rate barely pushing the high teens. There were fissures over language and ethnicity, particularly the now-violent split between Nuer and Dinka cadres of the army, along with an ominously low labor participation rate, and an alarming shortage of human capital.

For the past two years, South Sudan has been governed by former militants, with its major infrastructural projects heavily underwritten—and often undertaken—by foreign governments and development agencies. The pressures that South Sudan has faced in its first years of existence are steeper than those that have confronted all but a small handful of countries. And it has had to depend on politically inexperienced ex-guerillas to steer it through a period during which it’s threatened by aggressive neighbors, chronic underdevelopment, and general nationwide turmoil.

“These are guys who spent 30 years in the bush who feel more comfortable in the bush,” says Cameron Hudson, a former National Security Council staffer, and Chief of Staff to the U.S. special envoy to Sudan from 2009 to 2012. “As you can see from Kiir, they never got rid of their army uniforms.” Hudson says that in the run-up to independence, the U.S. and other Western partners helped the Juba government “balance their books and create the illusion of institutions. But the people running those institutions weren’t technocrats… and now it’s breaking down along ethnic lines that have always been there.”

Before this week, it was possible to forget all of this if one only focused on Juba, a city that had been developing at a breakneck pace when I visited South Sudan in March of 2012. Juba’s population had exploded, largely thanks to the end of the civil war and the arrival of migrant laborers from neighboring countries. The city had a network of freshly paved roads and even a small number of new multi-story buildings—significant developments for a place that had been a glorified Sudanese garrison town just a few years earlier. Residents told me that private vehicle ownership had once been nearly unheard of, but as the pastor of a local Anglican church said, “Even someone who never expected to have a car now finds himself driving.” At the time, this seemed like a perfect metaphor for South Sudan’s potential: with the threat of war eliminated and Khartoum off of its back, even the most mundane evidence of progress seemed to point toward a more peaceful future. The possibility of normalcy felt like a promising and even transformative development for a place where nearly two million people had been killed over a quarter-century of conflict.

A visitor could latch onto the center that was holding, as I did in early 2012: there were weeks that year in which hundreds of people were massacred in Jonglei state, but the violence never really made its way to Juba. Returnees were starving in squalid camps in Northern Bar al Ghazal state, and the Yida refugee camp in Unity state was bursting with people fleeing the fighting in Blue Nile and Southern Kordofan. But both of these places were a multi-day drive from the capital, and in my conversations with South Sudanese officials, I got the distinct sense that they believed the country’s future lay with the rest of Anglophone east Africa, places far easier to access from Juba than their own country’s restive hinterland. There was the appearance of order, and with it the appearance of compromise and moderation—endless summits with Khartoum and a stream of largely-cosmetic agreements.

Given the U.S. role in bringing about South Sudan’s independence—the decades of Congressional visits to rebel-held territory in the South and occasional hardball diplomacy with Khartoum—along with the Republic of Sudan’s brutal human rights record and very public alliances with Iran and Hamas, it was tempting and even necessary to believe that Juba’s tenuous calm actually meant something. That calm at least provided a basis for the state’s future viability, and it proved that South Sudan could meet some minimal standard of survival in the face of intense internal and external pressure. Stability—even fake stability—vindicated U.S. policy in Sudan, in which the Bush and Obama administrations prioritized the southern issue and counter-terror cooperation, often at the expense of human rights concerns in Darfur, Southern Kordofan and Blue Nile. (Rebecca Hamilton’s Fighting for Darfur offers a definitive account of U.S. Sudan policy during this period, when Obama and particularly Bush had to balance their South Sudan efforts against domestic activism concerning Khartoum’s human rights record).

The calm gave the U.S. an additional partner in a chaotic and strategic corner of Africa. That very same calm appears more fictitious by the hour. South Sudan was never stable. It was never on a trajectory toward becoming a normal Westphalian unit, and the ruling SPLM, whose members are more accustomed to a military hierarchy than to civilian governance, has done little to bring about an inclusive or even competent state structure.

It’s unclear what comes next, but the U.S. is hardly in a position to sit this one out. From one perspective, South Sudan represents the promise of an engaged and principled U.S Africa policy. Over several presidential administrations, the U.S. mobilized its diplomacy toward ending a destructive civil war, and creating conditions under which a Western-allied, democratic country could be cleaved from a hostile and anti-democratic one. The 2005 Comprehensive Peace Agreement hastened the end of a longstanding system of racial and religious discrimination, while South Sudan’s mere existence as an independent state makes it all but impossible for it to ever again be ruled from Khartoum. South Sudan’s independence seemed an ideal convergence of abstract principle—the defense of freedom and human rights, the promotion of democracy—with the U.S.’s strategic self-interest, a rare bright spot in America’s often lethargic and confused policy toward African countries.

This week implodes the notion that things were ever that simple. South Sudanese independence was indeed a major accomplishment, both for South Sudanese and for the diplomats and activists who pushed for a final resolution to Sudan’s civil war. But it is an incomplete accomplishment, and it’s early enough in its progress for any number of factors to speed its reversal. This presents an immediate policy dilemma: Supporting Kiir through a potential civil war effectively subsidizes the chaos of the post-independence period. At the opposite extreme, sanctions or total disengagement would be an abandonment unworthy of decades of Sudanese and American efforts.

It’s unclear whether the Obama administration is in a position to launch the kind of careful diplomacy that the moment requires. “The president himself has really distanced himself from Kiir personally,” says Hudson. “I think that over the course of the last few years, whatever leverage we might have had in Juba we essentially lost.” As Hudson notes, Kiir was a poor manager of his relationship with Washington—the decision to invade the disputed Heglig region in April of 2012 lost him some sympathy stateside, as has the corruption and heavy-handedness of his administration.

But Kiir also enjoyed a close relationship with Obama’s predecessor—the one who gave him the cowboy hat—which might have convinced Kiir that the US would be less conditional in its support for him. “They assumed they’d get the same treatment from Obama that they got from Bush,” says Hudson. “But the situation had changed dramatically. They were no longer the plucky rebels fighting the Khartoum government. They were going to have to stand on their own two feet.…They expected unfailing, unflinching friendship and support. And when it didn’t come they kind of rejected us, I think, and at the same time we rejected them.”

It would be ideal if the US had a robust presence on the ground during such a sensitive period, diplomats who could take advantage of the US’s formerly close relations with South Sudan’s fracturing ruling party. But on Wednesday, the US ordered an evacuation of both American citizens and non-emergency diplomatic personnel from Juba. In a time when the consequences of state collapse in East Africa have been felt in Somalia, the Central African Republic, and even upscale Nairobi shopping malls, US policymakers have Benghazi on their minds. It’s a troubling beginning to a crisis that already seems to be getting out of hand—a crisis that threatens one of US diplomacy’s few major successes in Africa.