Updated at 3:15 p.m. ET
The Pentagon said Thursday that an investigation into the deaths of four American soldiers in Niger last year found "individual, organizational and institutional failures." But it said no sole reason was responsible for the ambush.
The four Americans were part of a U.S. contingent that has been assisting Niger's military since 2013 in a battle against extremists linked to the Islamic State. A dozen Americans, along with members of Niger's military, came under attack by extremists on Oct. 4 of last year outside the remote southwestern village of Tongo Tongo.
"I take ownership of all the events connected to the ambush," Marine Corps Gen. Thomas Waldhauser, the head of U.S. Africa Command, said at the Pentagon as he discussed the investigation with reporters. "Again, the responsibility is mine."
The Americans left their base a day earlier, Oct. 3, on a routine mission to check in with village elders. But that turned into three separate missions over two days, and became more dangerous as the Americans headed to a site recently vacated by an extremist leader and his fighters.
However, the Americans "did not conduct pre-mission rehearsals or battle drills with their [Nigerien] partner force," the report said.
In addition, "this mission was not approved at the proper level of command," the Pentagon report said, adding that the change needed authorization at a U.S. battalion-level command, which is based in neighboring Chad.
After spending the night in the field, the U.S. forces began returning to their base on Oct. 4. They stopped in Tongo Tongo to get water and meet with village leaders. Shortly after they drove off in several military vehicles, the Americans and their Nigerien partners were ambushed by a much larger force.
"The American and Nigerien forces fought courageously despite being significantly outnumbered by the enemy," the report said.
The report cites multiple failures that include "a lack of attention to detail" in planning the mission and "inadequate notification" of higher levels of command. This contributed to a "general lack of situational awareness and command oversight at every echelon."
French Mirage jets showed up as the ambush was coming to an end, made several low passes and scattered the extremists, but did not fire. The report says that's because the pilots could not distinguish between friend and foe.
The four Americans killed were Staff Sgt. Bryan Black, Staff Sgt. Dustin Wright — both Green Berets — and Staff Sgt. Jeremiah Johnson and Sgt. La David Johnson. Two Americans were also wounded, and five Nigerien troops were killed.
Gen. Waldhauser said changes have been made in the wake of those deaths.
"We are now far more prudent on our missions," he said.
NPR Pentagon correspondent Tom Bowman spoke with a retired U.S. officer with experience in Africa. He said the American team should have planned better, should have had greater firepower, and needed to be in touch with a medevac helicopter and a quick reaction force in case something went wrong.
The U.S. forces in Niger are there to assist the national army but are not supposed to be directly involved in combat. However, missions can and do take them into dangerous areas where fighting breaks out.
The U.S. has some 20 military missions in Africa, mostly in the northern half of the continent. The one in Niger is one of the largest, with roughly 800 U.S. troops based there. Most of the Americans work on an existing drone base or on another one that is under construction, the Pentagon said.