The Pentagon on Thursday will release the final report on the Niger attack that killed four Americans last October, concluding that the Army Special Forces team did not get required command approval for the initial risky mission to go after a high-level insurgent linked to the Islamic State group.

Defense officials said they will lay out how the mission unfolded, leading to the gruesome ambush, and then explain what is being done to correct the problems brought to light by the incident. Families of the fallen troops have been briefed on the investigation, including details of their loved ones' final moments as they battled as many as 100 insurgents in a fierce firefight.

"The whole thing was a screwed-up mess," said Arnold Wright, father of Staff Sgt. Dustin Wright of Lyons, Georgia, who was killed in the attack. He said he's concerned that the Army may be pinning the blame on lower-ranking soldiers and not accepting responsibility high enough up the chain of command.

The briefing, he said, gave the impression "that the captain, the team leader, that he mischaracterized the mission" as one to reach out to local leaders rather than a mission to target the insurgent.

The Associated Press reported in early March that the team received information about the location of Doundou Chefou, who was suspected of involvement in the kidnapping an American aid worker, and acted on what they considered was a fleeting chance to get him. But the team did not disclose that mission to higher-level commanders, and instead outlined a lower-risk mission to meet with tribal leaders, U.S. officials told the AP. The officials spoke on condition of anonymity to discuss the investigation ahead of its release.

The report is expected to detail missteps in the mission's approval process and whether that contributed at all to the ambush that erupted many hours later. Its findings will put renewed focus on U.S. military activity in Africa, particularly the role of special operations forces who've been advising and working with local troops on the continent for years. Extremists linked to IS and al-Qaida carry out increasingly bold attacks in West Africa's vast Sahel region.

The investigation was led by U.S. Africa Command's chief of staff, Maj. Gen. Roger Cloutier Jr. Officials spent months trying to unravel the complex incident, conducting dozens of interviews across the U.S., Europe and Africa.

The Pentagon will also unveil recommended changes, including greater oversight to ensure proper mission approval and risk assessment, as well as improved security measures, more heavily armored vehicles, and better weapons and training, U.S. officials said.

Killed in the attack were: Army Sgt. La David T. Johnson, 25, of Miami Gardens, Florida; Staff Sgt. Bryan C. Black, 35, of Puyallup, Washington; Staff Sgt. Jeremiah W. Johnson, 39, of Springboro, Ohio; and Staff Sgt. Dustin M. Wright, 29, of Lyons, Georgia. Four Nigerien troops were killed and two American soldiers and eight Nigerien forces were wounded.

Officials have said the investigation doesn't draw a direct link between the team's failure to get appropriate approval of the initial kill or capture mission and the attack that came much later, once commanders had approved other changes to the mission. The team was called off before they got to the location where Chefou was believed to be, because he had left. The troops, however, were later sent to collect intelligence at a location where Chefou had been, and then they stopped at the village of Tongo Tongo for supplies before heading back to their base.

"They had a mission to go to a location that was like four hours away and they went on that mission and the target was gone," Wright told the AP in an interview, recounting what Cloutier told him. "They started back and they got like two hours or so from their home base and they got a change of mission to go to another location back north like four hours away to act as a blocking force for another team was coming in with helicopters to hit the target."

Bad weather forced the helicopters to abort, Wright said, and his son's team went on to the site, where they destroyed motorcycles, ammunition and other equipment before heading to Tongo Tongo.

After leaving the village, they were ambushed about 120 miles (200 kilometers) north of Niamey, Niger's capital, by as many as 100 Islamic State-linked militants carrying small arms and rocket-propelled grenade launchers.

Wright, an Army veteran, said he was told the troops tried to stand and fight, leaving their vehicles so they could use them for cover. But as fighting intensified and more enemy fighters came, the American-led team decided to flee, using smoke for cover.

The two U.S. trucks with machine guns went first, Wright said, leaving behind the truck his son Dustin was driving that had no mounted gun. As his son tried to get away, Wright said Staff Sgt. Black was firing from the front passenger seat and Staff Sgt. Jeremiah Johnson was shooting from the back of the truck. Then Black got shot.

"So Dustin stops the vehicle, runs around and grabs Bryan Black by collar and pulls him behind the vehicle," Wright said.

As Johnson tried to help Black, Dustin Wright fired across the hood of the truck. Wright said Black died and the vehicle was disabled, so his son and Johnson fled on foot. Johnson was shot and Dustin Wright got hit after running back to help Johnson. Both died.

La David Johnson became separated from the others as he fought and ran for cover in the brush. He was gunned down, but his body wasn't found until two days later.

The battle, said Arnold Wright, lasted 40 minutes or more.

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Bynum reported from Savannah, Georgia.