The ambush occurred on October 4, 2017 as a unit of 11 American special forces soldiers and 30 Nigerien troops, returning from a village near the Malian border, were overrun by scores of extremist fighters.

An investigative report released by the Pentagon in May said that while US soldiers had fought bravely and four "died with honor," they had not been properly prepared for the mission. Investigators cited "individual, organizational and institutional failures."

Those being disciplined, the Times said Saturday, include Captain Mike Perozeni, the leader of the Green Beret team, as well as his second in command, a master sergeant whose name has been withheld.

The paper said a letter of reprimand to Perozeni cited the insufficient training and a lack of mission rehearsals.

The two senior officers who approved the mission and oversaw the ill-fated operation were not reprimanded, according to the newspaper.

"As a result of the Niger 15-6 investigation report, Secretary Mattis directed US Africa Command, US Special Operations Command, Department of the Army and the Under Secretary of Defense for Personnel & Readiness to conduct a comprehensive review of procedures, policies and training programs and report back to him with a plan of action and corrective measures," said Commander Candice Tresch, a Pentagon spokeswoman.

"Secretary Mattis received those reports by the 120-day deadline and is conducting a thorough review of the findings."

The Defense Department has been tight-lipped about the nature of the mission in Niger -- the existence of which surprised many Americans.

The Times account said Perozeni's Green Beret unit, Team 3212, had headed toward the Niger-Mali border in pursuit of an Islamic State group leader named Doundoun Cheffou.

After intelligence located him, an operation was planned against the leader's camp by a helicopter-borne team of American commandos and Nigerien troops, along with Team 3212.

But bad weather led to the helicopter mission being canceled. Team 3212 proceeded to the now-empty campsite. It was ambushed by some 50 heavily armed Islamic State fighters while returning to its outpost.

The ambush claimed the largest loss of American lives in combat in Africa since the 1993 "Black Hawk Down" incident in Somalia.

It also touched off debate about the presence of the 800 American troops in Niger and the larger purpose of the US military in Africa.

General Thomas Waldhauser, head of Africa Command, said in May that US forces had since become "far more prudent" in their missions and had beefed up their firepower.