Tigray’s leader, Debretsion Gebremichael, interviewed by New York Times

GIJET, Ethiopia — The convoy sped down from the mountain, slipping and sliding on roads greasy from a recent shower of hailstones. As it descended toward the regional capital of Tigray, curling through rocky hills and remote hamlets, people clustered along the route in celebration.

Women stood ululating outside stone farmhouses, and fighters perched atop a ridge fired their weapons into the air as the vehicles curled around the detritus of battle: burned-out tanks, overturned trucks and a mucky field where on June 23 an Ethiopian military cargo plane, shot down by the Tigrayans, had smashed into the ground.

The leader of Tigray, Debretsion Gebremichael, was going home.

Two days earlier, his scrappy guerrilla force had retaken the regional capital, Mekelle, hours after Ethiopian troops suddenly abandoned the city. Now Mr. Debretsion, a former deputy prime minister of Ethiopia, was leaving the mountains where he had been ensconced for eight months leading a war to re-establish his rule over the region.

“I didn’t expect to make it back alive,” Mr. Debretsion said on Thursday night in an interview, his first since the fall of Mekelle. “But this isn’t personal. The most important thing is that my people are free — free from the invaders. They were living in hell, and now they can breathe again.”

The Tigrayan leader offered a rebel-side account of the conflict that has plunged Ethiopia into chaos since Nov. 4, when Prime Minister Abiy Ahmed ordered a military operation there. The civil war has led to the displacement of nearly two million people, and to widespread hunger and reports that civilians were subjected to atrocities and sexual violence.

Mr. Debretsion, who is believed to be in his late 50s, claimed to have crippled Ethiopia’s powerful army, defeating seven of its 12 divisions and killing at least 18,000 soldiers. He also detailed plans to expand the war across Tigray, in defiance of international calls for a cease-fire, until his fighters have expelled from the region every outside force, including Eritrean soldiers and ethnic Amhara militias.

“They have taken the land by force,” Mr. Debretsion said. “So we will take it back by force.”

When we arrived for the interview, on a stormy late afternoon, to a fortresslike house in Mekelle, Mr. Debretsion was working on a laptop in a nearly dark upstairs bedroom. The government had cut the power to the city and shut down its phone network.

Barely visible in the gloom, Mr. Debretsion apologized for the circumstances. Tigray was “under siege,” he said, criticizing Mr. Abiy — a onetime political ally — as an impetuous and inexperienced leader who had overreached.

Billene Seyoum, a spokeswoman for Mr. Abiy, did not respond to requests for comment.

On Friday, the Tigray Defense Forces mounted a spectacle that seemed intended to humiliate Ethiopia’s leader. The fighters marched at least 6,000 Ethiopian prisoners of war through downtown Mekelle past residents chanting, “Abiy is a thief!” A woman holding a large photograph of Mr. Debretsion led the procession.

The Tigrayan leader fought his first war in the 1980s as the head of a guerrilla radio station for the Tigray People’s Liberation Front, a rebel group leading the resistance against a brutal Marxist dictatorship in Ethiopia.

The rebels swept to power in 1991, with the Tigrayan leadership at the head of a governing coalition that dominated Ethiopia for nearly three decades until Mr. Abiy became prime minister in 2018.

In power, the Tigrayan leadership stabilized Ethiopia and achieved soaring economic growth for nearly a decade. But progress came at the cost of basic civil rights. Critics were imprisoned or exiled, torture was commonplace in detention centers and the Tigray People’s Liberation Front won successive elections with a reported 100 percent of the vote.

By then, Mr. Debretsion had a reputation as a low-key technocrat. He served as communications minister and headed Ethiopia’s power utility, where he oversaw construction of a $4.5 million hydroelectric dam that, when completed, will be Africa’s largest.

But as popular protests against the Tigrayan leadership’s rule roiled Ethiopia from 2015, and as the police killed hundreds of protesters, Mr. Debretsion rose in prominence inside the party. Analysts say he was seen as a younger and more moderate figure than those steeped in Tigrayan nationalism who had dominated the party for decades.

The eruption of war changed everything.

Mr. Abiy said he had no choice but to launch military action, after months of escalating political tensions, when Tigrayan forces attacked a military base on Nov. 4.

Mr. Debretsion challenged that account, saying that Ethiopian troops had been massing on Tigray’s borders for days in preparation for an assault. He had advance knowledge of those plans, Mr. Debretsion said, because ethnic Tigrayans accounted for more than 40 percent of senior Ethiopian military officers, and many defected in the early days of the fight.

At first, Tigrayan forces were caught off guard by a barrage of drone strikes against artillery and supply lines that he said were conducted by the United Arab Emirates, an ally of both Mr. Abiy and the leader of Eritrea, Isaias Afwerki.

An Emirates spokesman did not respond to questions about the alleged drone strikes. Mr. Debretsion said they had changed the course of the war.

“Without the drones,” he said, “the fight would have been different.”

The Tigrayans, buoyed by a huge influx of new recruits, mounted their dramatic comeback just before Ethiopia’s election on June 21.

With the vote canceled in Tigray, Ethiopian forces attacked the T.D.F. at its stronghold in the Tembien mountains, west of Mekelle. The Tigrayans struck back hard, and within days several Ethiopian bases had been overrun and thousands of Ethiopian soldiers were captured.

Mr. Debretsion said he would free most of the Ethiopian prisoners who were marched through Mekelle on Friday, but would continue to detain the Ethiopian officers.

He called on the international community to ensure accountability for the spree of atrocities reportedly committed in Tigray in recent months — massacres, rape, the use of starvation as a weapon of war. Some Tigrayans had also been accused of atrocities during the conflict. But Mr. Debretsion rejected a United Nations-led investigation that is being conducted alongside a rights body linked to the Ethiopian government.

“It’s very clear they are partial,” he said.

He warned that if Mr. Abiy tried to mass forces in regions bordering Tigray again, he would quickly send fighters to intercept them.

In recent days, some Tigrayan leaders have suggested that troops could march on Asmara, Eritrea’s capital, to oust Mr. Afwerki, who harbors a decades-old enmity with them.

Mr. Debretsion sounded a more cautious note. Tigrayan troops would fight to push Eritrean troops over the border, he said, but not necessarily go farther.

The euphoric mood that gripped Mekelle this past week, with some fighters rushing to be with families and others celebrating in the city’s restaurants and nightclubs, is also a challenge for Mr. Debretsion.

The mood might be deflated in the coming weeks, as shortages of food and fuel hit Mekelle, now isolated on all sides.

Aid groups say that more vulnerable Tigrayans may starve if Mr. Abiy’s government does not allow vital aid deliveries.

Even if the conflict ends soon, Mr. Debretsion said, Tigray’s future as part of Ethiopia is in doubt. “The trust has broken completely,” he said. “If they don’t want us, why should we stay?”

Still, he added, nothing has been decided: “It depends on the politics at the center.”