(Bloomberg Opinion) -- We may be long past holding laureates of the Nobel Peace Prize to its lofty standards — the cruel cynicism of Henry Kissinger and open bigotry of Aung San Suu Kyi are just two instances of honorees behaving dishonorably — but Abiy Ahmed’s belly flop from the pedestal is nonetheless remarkable. In less than a year since his uplift in Oslo, Ethiopia’s prime minister has embroiled his country in a civil war and brought the Horn of Africa to the edge of chaos.

If Abiy cannot pull back from the precipice, his confrontation with the leadership of the northern region of Tigray will reverse the gains from years of growth and investment that have made Ethiopia’s economy the envy of the continent.

Long-simmering tensions between the central government and the Tigrayans, a minority ethnic group that once dominated Ethiopian politics, have boiled over. In early November, Abiy ordered government forces to attack the restive northern region of Tigray, blaming its leaders for a strike on an army base.

As the fighting has escalated, Abiy and Debretsion Gebremichael, president of the Tigray region, have painted themselves into opposite corners. The prime minister has vowed not to stand down his forces until all weapons in Tigrayan hands have been destroyed. He is resisting international calls for mediation. Debretsion has boasted that his fighters, thought to be 250,000-strong, “cannot be beaten.”

For all his promises of a swift victory, Abiy now faces a protracted civil war that could suck in other ethnic groups — or, to quote from his acceptance speech in Oslo last December, “brothers slaughtering brothers on the battlefield.”

The death toll is in the hundreds and rising fast. There have been reports of war crimes against non-Tigrayans in the north, and political score-settling against Tigrayans in Addis Ababa. United Nations officials warn that “the risk of atrocity crimes” is growing.

The conflict has already spilled over Ethiopia’s borders, and thousands have fled the fighting into neighboring Sudan. Debretsion has accused another neighbor, Eritrea, of joining forces with the Ethiopian military, and has launched rockets at the Eritrean capital of Asmara.

There are also dangerous consequences for a third neighbor: To strengthen his forces against the Tigrayans, Abiy has withdrawn thousands of Ethiopian peacekeepers from Somalia, where they were fighting an Islamist insurgency. This diversion comes even as the Trump administration is contemplating a drawdown of forces from Somalia.

Hopes for stability and prosperity in the Horn of Africa rest substantially on Ethiopia’s ability to maintain internal equilibrium, keep peace with its neighbors and act as the region’s economic engine. The first of these challenges was always going to be the hardest. Abiy’s appointment in 2018 ended three decades of rule by the Tigray People’s Liberation Front. (The prime minister is from the Oromo, the largest ethnic group.)

It was inevitable that Abiy’s political and economic reforms would reduce Tigrayan influence, and just as inevitable that the northerners would receive this poorly. But they are not the only ethnic group feeling hard done by: The Amhara and Somali — second- and third-largest — have grievances of their own. And over the summer, Oromo anger over the murder of a popular singer led to violence.

The prime minister responded by imposing authoritarian restrictions and jailing political opponents and journalists. Whether general elections, scheduled for late August but postponed because of the coronavirus pandemic, would have deepened the ethno-political divide or given Abiy a national mandate to rule is an open question.

The Tigrayans went ahead with regional elections, which Addis Ababa dismissed as invalid. But the high turnout gave the regional government more credibility than the prime minister can muster, and it strengthened Tigrayan demands for greater autonomy — a direct challenge to Abiy, who wants greater authority for the central government.

With other regions closely following the outcome of the confrontation, the prime minister will be loath to show leniency. Reports suggest his government has sacked or suspended scores of Tigrayans from positions in the bureaucracy and military. This purging will likely deepen the northerners’ determination to fight on, and force the Nobel laureate even further into ignobleness.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Bobby Ghosh is a Bloomberg Opinion columnist. He writes on foreign affairs, with a special focus on the Middle East and Africa.

©2020 Bloomberg L.P.