"I have concluded that we need to conduct a comprehensive review to ensure that accountability for this event is met and that the complete picture is provided to the American people," Hegseth wrote in a memo.

A special review panel will "thoroughly examine previous investigations, to include but not limited to, findings of fact, sources, witnesses, and analyze the decision making that led to one of America's darkest and deadliest international moments," the memo said.

"This team will ensure ACCOUNTABILITY to the American people and the warfighters of our great Nation," it added.

The US withdrawal saw Taliban fighters sweep aside Afghan forces, forcing the last American troops to mount an evacuation from Kabul's airport that got more than 120,000 people out of the country in a matter of days.

On August 26, 2021, a suicide bomber targeted crowds of people on the perimeter of Kabul airport who were desperate to get on a flight out of the country, killing more than 170 people, among them 13 American troops.

Joe Biden, who was US president during the withdrawal, defended the decision to leave Afghanistan, which critics have said helped cause the catastrophic collapse of Afghan forces.

That paved the way for the Taliban to return to power two decades after their first government was toppled by American forces in the wake of the September 11 attacks.