ADDIS ABABA, Ethiopia — The announcement last week that the government was about to launch a military operation into one of the country’s regions came, to put it lightly, as a shock.

Not only was it very far from the emollient statecraft that won Prime Minister Abiy Ahmed the Nobel Peace Prize last year, it also seemed to shatter the purpose of his premiership. When he rose to power in 2018, Mr. Abiy promised to guide Ethiopia into a new era of peace, prosperity and national reconciliation.

But on Nov. 4, he dispatched the Army to Tigray, one of the country’s 10 semiautonomous regions and home to roughly 6 percent of the population, accusing its leaders — with whom he has increasingly sparred — of attacking a government defense post and attempting to steal military equipment.

And in the days since, Mr. Abiy imposed a six-month state of emergency on the Tigray region, declared its legislature void and approved a provisional replacement. As fighting raged, the internet and telephone networks have been shut down. Hundreds are reported to be dead.

This is a tragedy. Ethiopia stands on the cusp of civil war, bringing devastation to both the country and the wider region. While the situation is volatile and uncertain, this much is clear: Mr. Abiy’s political project, to bring together the nation in a process of democratization, is over. And much of the blame must be laid at his door.