A French drone strike killed a top Islamic State militant believed to be the mastermind of attacks in Niger that claimed the lives of four U.S. soldiers in 2017 and six French aid workers last year.

The August operation, which was months in the making, with drone strikes and commando assaults in a lawless region on the border between Mali and Niger, targeted Adnan Abu Walid al-Sahrawi, the leader of the Islamic State in the Greater Sahara.

“His death deals a decisive blow to the leadership of the Islamic State in the Sahel,” France’s armed forces minister, Florence Parly, told a news conference on Thursday, referring to the arid region south of the Sahara Desert. “They will without a doubt have trouble replacing him.”

The operation from Aug. 17 to Aug. 20 involved cooperation with local and European forces, as well as the U.S. military, she said.

Special forces hit positions based on information from two captured Islamic State members close to Sahrawi. Drones and fighter jets killed about a dozen militants, while 20 soldiers stormed a hideout in a forest near the border, said Gen. Thierry Burkhard, the French army’s chief of staff.

One of two people riding on the back of a motorcycle hit by a drone strike appeared to be the Islamic State leader, he said.

Rumors of Sahrawi’s death had circulated for weeks before President Emmanuel Macron’s Twitter announcement late Wednesday that he was “neutralized by French forces.” The Islamic State leader, who was 48, was born in the disputed territory of Western Sahara and became an al-Qaeda ally. He switched allegiance to the Islamic State in 2015 and founded its affiliate in the Sahel region of West Africa.

The affiliate, which operates mainly in Mali, Burkina Faso and Niger, has targeted U.S. and French military personnel there. In one of its most notable attacks, in October 2017, a U.S. Special Forces team carrying out reconnaissance in Niger was caught in a deadly ambush by militants armed with machine guns, small arms and rockets.

Four U.S. soldiers were killed and two others wounded in the ensuing firefight. At least four Nigerien troops also died. The Islamic State in the Greater Sahara was the Trump administration’s primary suspect for the ambush, and Sahrawi himself claimed responsibility. The State Department’s Rewards for Justice program offered $5 million for information leading to his capture.

The 2017 mission ignited a political firestorm in the United States at the time, raising questions about the U.S. military’s broader mission in Africa and why one of the fallen soldiers, Sgt. La David Johnson, was not recovered for two days, The Washington Post previously reported.

Sahrawi’s militants were also behind the murder of six French aid workers, along with their driver and a local guide, who were visiting a wildlife reserve in Niger in the summer of 2020.

France has blamed the group for the deaths of about 2,000 to 3,000 civilians in the region since 2013, “and to be precise, the large majority of them were Muslims,” the armed forces minister said Thursday.

Sahrawi’s death follows plans by France to slash its military presence in West Africa by about half over the next year. ​​The former colonial power, which continues to have close political and cultural ties with West African countries, has long led one of the biggest forces in the fight against extremist groups in the region. But the mission has become unpopular in both France and West Africa.

France has about 5,100 troops in West Africa, the most of any overseas partner. Three military bases are slated to close in Mali’s north, the heart of the crisis. Analysts have previously warned that the decision to draw down French troops will upend the international community’s response to the menace of extremism.

Those concerns have been heightened after the chaotic withdrawal of U.S. troops from Afghanistan last month, which has buoyed local extremists hoping for a Taliban-style victory in the region.

Fighters across the continent — many of whom have professed loyalty to al-Qaeda and the Islamic State — have publicly celebrated the Taliban’s takeover as the result of perseverance against the United States and other Western armed forces.

“We will continue to wage this battle. We will not abandon the Sahel,” Parly insisted at the news conference.

Her comments also came hours after news broke that the United States and Britain will share highly sensitive nuclear submarine technology with Australia, a surprise move that sunk Paris’s own defense deal and that the minister called at the conference “very bad news.”

Danielle Paquette in Dakar, Senegal, and Rick Noack in Paris contributed to this report.

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