NAIROBI, Kenya >> As fighting flared in northern Ethiopia last month, shattering a five-month truce and reigniting a destructive civil war, a small U.S. military aircraft carrying senior American diplomats crossed the front line on a secret mission to halt the bloodshed.

Flying low and taking measures to avoid detection, the jet traveled to Tigray, the besieged northern region that has been at war with the Ethiopian government of Prime Minister Abiy Ahmed, before continuing to Djibouti for a round of tense peace talks, according to people familiar with the negotiations. In a measure of the distrust between the two sides, Mike Hammer, the American envoy to the region, flew aboard the U.S. Air Force plane as an assurance that it would not be shot down.

Tigray is the world’s unseen war, a sprawling conflict hidden behind a punishing government siege that has severed communications in the region, locked out reporters and left 5.2 million people in urgent need of food aid. United Nations investigators have called it a war crime.

But in recent weeks the fighting has surged to its most intense level yet — and the secret efforts at peace have given way to raging combat that many fear could quickly spiral across the Horn of Africa, destabilizing the region.

While the world’s gaze is largely fixed on the war in Ukraine, the conflict in Tigray is also huge, with three major armed forces, including two of Africa’s largest armies, those of Ethiopia and of Eritrea, battling on multiple fronts across a rugged region twice the size of Switzerland.

The latest fighting, featuring pitched battles, drone strikes and artillery barrages, has pulled in neighboring countries and involves hundreds of thousands of combatants, by most estimates. At least a hundred civilians have died and as many as 500,000 have fled their homes in recent weeks, a senior U.N. official said.

A diplomatic drive to end the war has also been hidden. An official peace process led by the African Union has been hobbled by disputes over mediators and money for most of the past year, officials say, prompting Western officials to try to carry the ball. Since March, the United States has held three secret meetings outside Ethiopia — in Djibouti and in the Seychelles — bringing together warring leaders for the first time since the war erupted in November 2020.

Details of the latest meeting on Sept. 9, which was attended by Abiy’s national security adviser, Redwan Hussien, and his justice minister, Gedion Timothewos, were provided by Western and Tigrayan officials who spoke on the condition of anonymity to discuss events that the Americans insisted should remain confidential.

A U.S. official confirmed that a U.S. Air Force Beechcraft aircraft had operated the flight across Tigray on behalf of the State Department.

Now hopes for peace lie with a surprise announcement this past week by the African Union, inviting both sides to talks in South Africa.

But the prospects for that initiative are uncertain. Tigrayan leaders have accused the mediator, the former Nigerian President Olusegun Obasanjo, of siding with Abiy. After initially scheduling talks for this weekend, the African Union said on Thursday only that they would take place “soon.”

Events on the battlefield could move faster than that.

Reliable information about the last six weeks of fighting is hard to obtain. But interviews with Western and Tigrayan officials — as well as video footage, satellite images and witness accounts gathered over the region’s few working phone lines — offered a keyhole view of a metastasizing conflict that is exacting a high cost on civilians.

Ethiopian drone strikes hit a kindergarten in August, killing several children, and a U.N. food truck in late September. An airstrike on Tuesday in Adi Da’ero, near the border with Eritrea, hit a center for refugees, killing at least 50 people, said two humanitarian officials in the area who spoke on the condition of anonymity for their safety.

After an earlier strike on the same town, video footage showed the lifeless body of a woman being pulled from smoking rubble.

“The fighting is intense, and the casualties are immense,” Gen. Tsadkan Gebretensae, a former chief of the Ethiopian military, now a strategist for the Tigrayans, said in a phone interview.

A spokeswoman for Abiy and spokesmen for the Ethiopian government and military did not respond to requests for comment. The government has denied it strikes civilian targets.

The most striking change in recent weeks is the return to the war of Isaias Afwerki, the dictatorial leader of the nation to the north, Eritrea, and his army, one of the largest in Africa, which was accused of many atrocities in earlier fighting.

Eritrean troops have pounded Tigray with artillery barrages from across the border and captured the Tigrayan town of Shiraro, where recent satellite images showed hundreds of marching soldiers and lines of artillery field guns. In an unusual move, several thousand Ethiopian soldiers have been flown into Eritrea to help with the assault, officials said.

Inside Eritrea, the country has “fully mobilized its armed forces,” calling all men below the age of 55 to military service, Annette Weber, the European Union envoy to the Horn of Africa, wrote to EU member states last month in a confidential briefing obtained by The New York Times.

“The war rages on with high military buildup on all sides, increased intensity and Eritrean participation,” Weber wrote in the leaked briefing, which first appeared on the website of the World Peace Foundation, a program at Tufts University.

“Tens of thousands are injured or killed on the various battlefronts, many with the belief that surrender is no option,” the briefing continued. “Much is at stake.”

The stakes for civilians in northern Ethiopia were outlined in a Sept. 22 report by U.N. investigators that accused both sides of war crimes, including massacres and sexual assaults. But it singled out Abiy’s forces for “using starvation as a method of warfare” and for “sexual slavery” of Tigrayan women held in military camps.

At Tigray’s largest hospital, doctors say that patients are dying from cancer, kidney disease and other treatable conditions for want of medicines. A recent study found that newborn babies in Tigray are dying at four times the prewar rate.

“One day we will be free of the fear of being bombed from the air,” Dr. Fasika Amdeslaise, a surgeon in Tigray with rare internet access, wrote on Twitter. “One day we will be able to treat our patients.”

The fighting is the latest twist of a war in which the fortunes of both sides have oscillated wildly.

Just a year ago, Tigrayan fighters were marching on the Ethiopian capital, Addis Ababa, after driving government forces from Tigray. But in November they were forced to retreat after Abiy obtained armed drones from Turkey, the United Arab Emirates and China.

The United States changed tack in January when President Joe Biden made his first phone call to Abiy, easing the Ethiopian leader’s fears that the United States intended to try to oust him, and setting the stage for secret talks, two American officials said.

Two months later, on March 10, a U.S. Army Beechcraft airplane carried Tsadkan, the Tigrayan general, to the Seychelles, where he met in a hotel with Field Marshal Birhanu Jula, the head of the Ethiopian military.

The two men hammered out a humanitarian truce that, weeks later, allowed aid convoys to roll back into Tigray. A second American-brokered meeting took place in Djibouti in June.

But the truce was also an opportunity for both sides to rearm, and as the summer wore on, Abiy appeared to drag his feet, officials said. His delegates at talks lacked the authority to make decisions, and he appeared reluctant to restore essential services like electricity and banking to Tigray.

The slide back to war on Aug. 24 prompted criticism from experts who say the Biden administration failed to apply enough pressure to force the warring groups to substantive peace talks.

“The diplomacy is clearly not working,” said Cameron Hudson, a former State Department official now affiliated with the Center for Strategic and International Studies. “There’s a lot of effort but they are not achieving anything. So we have to question if we’re using the right tools.”

The reemergence of Isaias, the Eritrean leader, adds a volatile new element to the conflict. On Sept. 20 Hammer, the American envoy, called for Eritreans to return home from the fighting in Tigray.

Other countries in the region are also getting sucked in — as well as a contingent of U.N. peacekeepers.

Sudan has been a “conduit” for flights carrying arms to Tigray, Weber said in her confidential briefing. In May, about 650 ethnic Tigrayans, on U.N. peacekeeping duty in Sudan, deserted the Ethiopian army and sought asylum, said two U.N. officials in Sudan who spoke anonymously because of the sensitivity of the situation. By August, about 400 of those peacekeepers had vanished, the officials said, mostly into Tigray to fight alongside refugees who had been recruited from camps along the border.

Hudson, the analyst, said it seemed that Washington was hesitating to take harder action, for instance deploying sanctions that Biden authorized in November, in the hope that Ethiopia might once again become a strong American partner in the region.

But with Ethiopia straining to the breaking point from the war in Tigray, as well as violent strife in other regions like Oromia, such a notion is “delusional,” Hudson said.

“We’re not going back to those old days, and certainly not under Abiy,” he said.

This article originally appeared in The New York Times.

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