Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE, on Thursday, met with troops at the U.S. naval base at Guantánamo Bay, Cuba, according to The Associated Press.

Mattis became the first Defense chief since 2002 to take a trip to Guantánamo. He did not tour the detention facility there or discuss the Trump administration's policies regarding its detainees, the AP reported.

The prison at Guantánamo has been used to hold suspected terrorists, and 41 detainees are currently held at the facility. Ten of those detainees have been charged by a military commission, according to the AP, and five have been cleared to leave.

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The Trump administration has not released any detainees from the prison or cleared any others to leave.

Former President Obama vowed to close the facility and transfer remaining detainees to the U.S. mainland, but was blocked by Congress. The Obama administration, though, sharply reduced the number of inmates from 242 to 41.

On the campaign trail, President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE said he intended to leave the prison open, and suggested he would increase the number of detainees held at the facility.

Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE visited the detention facility in July.