President George W. Bush meets with Salva Kiir, who was then Sudan's first vice president and is now South Sudan's president, at the White House in January 2009. (J. Scott Applewhite/AP)

Saturday was the fifth birthday of the world's youngest country. But instead of celebrations in South Sudan's capital, Juba, there was fierce battle. Reports put the death toll at more than 300, but accurate figures are hard to come by amid the chaos. The U.N. Security Council held a meeting behind closed doors on Sunday to discuss the situation. More than 160,000 South Sudanese already live in displacement camps.

This is not new. War has been a constant for decades in South Sudan. But it was not the future envisioned by the American diplomats and politicians who played a critical role in bringing about South Sudan's independence.

For decades, U.S. officials took on an outsize role in South Sudan's negotiations with Sudan, seeking to create an African "success story" for their legacies. It was also a way to exact punishment on Sudanese President Omar Hassan al-Bashir, who has been accused of genocide in the western region of Darfur and relentless suppression of resistance in South Kordofan state, the oil-rich Abyei region, Blue Nile state and the Nuba Mountains — all border areas between the north and the south. Internal ethnic tension in the predominantly black south aren't a post-independence creation, but the United States may have underestimated the depth of the divisions while focusing on independence from the Arab-dominated north.

My colleagues Sudarsan Raghavan and Anne Gearan described the U.S. involvement in a 2014 article:

South Sudan owes its existence to the United States.

Years of diplomacy and development aid by successive U.S. administrations helped create the world’s newest nation three years ago. South Sudan was supposed to break the sad, familiar African model of petty rivalries, corruption and oppression. The country has ample oil resources and eager international investors.

But as a conflict fueled by ethnic and personal power struggles tears the country apart, the United States has been unable to pull South Sudan from the brink of civil war.

Much the same can be said in mid-2016. The "personal power struggle" between Salva Kiir and Riek Machar, leaders of the country's two largest ethnic groups, the Dinka and the Nuer, respectively, again threatens to plunge South Sudan into civil war. For what it's worth, the two men were actually meeting in Juba when the violence broke out, trying to finagle a peace agreement after years of bloodshed. Both called for calm, but it seems neither has much control over the situation. There is also not much trust between them — the last war broke out when Kiir accused Machar of plotting a coup.

In a pointed statement, a Machar spokesman said this weekend's events mean that the country is "back to war."

Critics of U.S. involvement have said that its officials may have been so happy to have helped South Sudan achieve independence that they neglected to follow up with continued mediation between the rival leaders. They also point out that the United States balked on imposing sanctions on those leaders once violence picked up. On the other hand, the United States is far and away the country that provides the largest amount of aid to South Sudan.

All told, those considerations may overplay the United States' ability to influence internal politics there. If this weekend was any indication, it is unlikely as ever that South Sudan will emerge from war while Kiir and Machar stay in power.

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