Eleven Yemeni detainees have been transferred to Oman from the US military prison at Guantanamo Bay.

The move leaves 15 detainees in Cuban prisons, the lowest number in the country’s history.

In a statement, the U.S. Department of Defense thanked Oman for supporting U.S. efforts “committed to responsibly reducing the detainee population and ultimately closing” the facility.

Those arrested after the 9/11 terrorist attacks were not charged with any crime during more than two decades in custody.

The transfer reportedly took place in the early hours of Monday morning, days after Khalid Sheikh Mohammed, who is accused of masterminding the Sept. 11, 2001, attacks on the United States, planned to plead guilty after joining federal Officials struck a deal to avoid the death penalty.

Monday’s transfer of Yemeni detainees is the largest to a single country under President Joe Biden.

Efforts to resettle the men in Oman began several years ago, but the United States says the situation in Yemen, which is mired in civil war, is too unstable to repatriate.

Those transferred from Guantanamo include Moath al-Alwi, who was released in 2022 and is known for building model ships from items found in prison, and Shaqawi al Hajj ), who went on multiple hunger strikes to protest his detention.

The Pentagon said the transfer was approved by a federal national security review panel, which determined that doing so was “in the national security interest of the United States.”

The transfer comes less than a week after Ridah Bin Saleh al-Yazidi, one of the prison’s original detainees, was deported to Tunisia in January 2002.

The Defense Department said three of the remaining 15 detainees were also eligible for transfer.

The military prison is part of a U.S. naval base complex in southeastern Cuba. The prison was established by the Bush administration in 2002 after the 9/11 attacks to house suspects captured during counterterrorism operations. At its peak, approximately 800 detainees were held here.

The controversy centers on the treatment of the detainees and how long they were held without charge.

As president, Barack Obama pledged to close prisons during his term. He said the prison violated American values ​​and undermined America’s standing in the world – a standing built on support for the rule of law.

Obama, who left office in 2017, also argued that the group’s presence harmed partnerships with countries that needed to help the U.S. fight terrorism and fueled jihadist recruitment.

But while in office, Obama faced congressional opposition to closing prisons — some stemming from questions about the fate of existing prison inmates. He transferred or ordered the release of more than 100 detainees to other countries.

The U.S. Congress has not allowed the transfer of detainees to U.S. states and blocked their transfers to certain countries, including countries with ongoing conflicts such as Yemen.

Efforts to reduce prison populations and close prisons stalled under Donald Trump, who signed an executive order to keep prisons open during his first term. Trump said efforts to release detainees or close facilities made the United States look weak on terrorism.

Since taking office in 2021, President Joe Biden has been working to move more detainees from the facility in hopes of closing it — though that seems unlikely until Trump takes office later this month .