(LONDON) -- French officials announced overnight that their military forces had killed the top ISIS leader in Africa, a terrorist for whom the United States had offered a $5 million reward due to his connection to the deadly attack on a team of Green Berets in Niger four years ago.
French President Emmanuel Macron announced on Twitter that Adnan Abou Walid al-Sahrawi, the leader of the Islamic State in the Greater Sahara, was "neutralized by French forces."
"This is another major success in our fight against terrorist groups in the Sahel," Macron said of the region in northwest Africa.
The drone strike occurred in late August but al-Sahrawi's death was confirmed this month, French and U.S. counterterrorism officials told ABC News.
Al-Sahrawi was wanted by the U.S. for leading the group of more than 100 militants responsible for attacking Operational Detachment-Alpha 3212, a team of soldiers from 3rd Special Forces Group on Oct. 4, 2017, leaving four Americans and at least six Nigerien soldiers dead outside the tiny village of Tongo Tongo.
The 2017 ambush is the subject of a four-year ABC News investigation and an ABC Documentaries film set for release on Hulu in November, "3212 UN-REDACTED: An Ambush In Africa. The Pentagon’s Betrayal."
Macron did not explicitly say that France's anti-insurgent Task Force Barkhane in Mali had been assisted by U.S. intelligence, but sources in Paris and in Africa confirmed that was the case. American intelligence had previously assisted in numerous raids carried out by French Special Forces in 2018 that killed many of the Tongo Tongo attackers and recovered American weapons and one vehicle from the Green Beret team attacked in 2017.
The parents of U.S. Army Sgt. 1st Class Jeremiah Johnson, who was killed in action in the 2017 attack and decorated with the Bronze Star Medal with "V" for Valor, praised the French but said the U.S. should have taken the lead on al-Sahrawi's capture or killing.
"We are profoundly grateful to the French Armed Forces for removing this threat to West Africa. At the same time, we are disappointed that the United States did not exert the effort to bring this individual to justice," Johnson's mother and stepfather, Debbie and Ray Gannon, told ABC News in a statement. "We should have made the effort to either kill or capture the individuals who were responsible for the ambush of ODA 3212 ourselves, instead of relying on other countries."
Also killed in the 2017 attack were Staff Sgt. Dustin Wright of Lyons, Georgia, Sgt. LaDavid Johnson of Miami, and Staff Sgt. Bryan Black of Puyallup, Washington.
"More death does not make losing Bryan any better. But knowing there is one less evil man in this world brings me peace," said Michelle Black, who authored the book "Sacrifice: A Gold Star Widow's Fight For The Truth," about her husband and the Tongo Tongo gunfight. "Perhaps it will prevent other families from suffering terror at his hands and for me that is enough."
Bryan Black's parents, Henry and Karen Black, also were grateful for the French operation, she said.
In a ceremony for all four families of the fallen soldiers in July, LaDavid Johnson and Jeremiah Johnson, both support soldiers who were killed with the Green Beret team, were posthumously inducted into the Green Berets.
"Although nothing can take away the pain of losing our four fallen heroes, there is comfort in knowing that justice has been served," said former Green Beret Maj. Alan Van Saun, who was company commander of the ambushed detachment ODA 3212, and who appears in the ABC documentary film.
"I am grateful for our French and African partners who worked tirelessly to bring this chapter to an end, but I know there is still a lot of work to be done to bring stability to the Sahel," Van Saun told ABC News.
The French Defense Ministry said that the operation was conducted between Aug. 17-22, in partnership with the Malian armed forces, against ISIS fighters in the dangerous forest area south of the village of In Delimane in Mali's Liptako region.
A senior French commander told ABC News that al-Sahrawi was "weakened after the loss of two of his logistics commanders in the same period," after the French neutralized Rhissa al-Sarhaoui and the commander known as Ikarey.
The French commander told ABC News that, based on U.S. intelligence, "we understood al-Sahrawi left Menaka on a motorbike and was about to cross the Nigerien border."
Al-Sahrawi was then targeted by a drone airstrike that killed the ISIS leader and resulted in the captured of ten of his men, French and U.S. officials said.
"This zone is a red one. Almost a stateless area. This is a huge get and could rebalance the power at least for the Malian Liptako," said the French commander, who added that confirming al-Sahrawi's death "took several weeks."
"The killing of al-Sahrawi follows a series of tactical successes by the French, who recently killed or captured several senior ISGS [Islamic State in the Greater Sahara] commanders," said Sahel expert Heni Nsaibia of the risk consultancy firm Menastream. "It appears that these events and the question of who will succeed al-Sahrawi have created serious tensions within ISGS. We are talking about numerous No. 1- and 2-ranking commanders eliminated in just months. This means that it will be difficult for the group to effectively restructure and reorganize at this point."
In a statement, Macron paid tribute to France's fallen troops in northwest Africa.
"The Nation is thinking this evening of all its heroes who died for France in the Sahel ... of the bereaved families, of all of its wounded," Macron said. "Their sacrifice is not in vain. With our African, European and American partners, we will continue this fight."