Khalid Sheikh Mohammed, the Pakistani national characterized as the mastermind behind the September 11, 2001, attacks on New York and the Pentagon, was arrested in 2003 and transferred to the U.S. military prison at Guantanamo Bay, where he has been held since 2006.

He has agreed to plead guilty after negotiations, along with two of his fellow detainees, the U.S. Department of Defense announced on Wednesday.

Although the Pentagon avoided providing details, the agreement allows Khalid Sheikh Mohammed to avoid trial, where he faced the risk of the death penalty, and instead will serve a life sentence, as clarified by the New York Times.

The two co-defendants involved in the agreement are Walid bin Attash and Mustafa al-Hawsawi.

All three have been detained for the past two decades at the Guantanamo prison in Cuba, on territory leased indefinitely to the U.S. since 1903.

All three faced charges of terrorism and the murder of nearly 3,000 people in the attacks on New York and Washington.

They were never tried: their prosecution was likely to face obstacles, especially due to information obtained through systematic torture they endured in CIA secret prisons.

In March 2022, the defense attorneys for the prisoners confirmed that negotiations were ongoing to agree on their sentences to avoid a trial before a military tribunal.

The defendants requested and received assurances that they would remain in the Guantanamo naval base prison and would not be transferred to a federal prison in the continental U.S., where they would serve their sentences in isolation.