GUANTANAMO BAY NAVY BASE, Cuba -- Earlier this month, in a drill shrouded in secrecy, prison guards practiced for something that hasn't actually happened at Guantanamo in a decade. They rehearsed receiving a new war-on-terror detainee.

Medical evaluation? Check. Notification of the International Red Cross? Check. Assignment to a cell? Check. Security and more security. Gone are the iconic orange uniforms that made Camp X-Ray infamous. The man who played the role of new captive wore white.

Navy Rear Adm. John Ring, the prison commander, says he hasn't gotten any word that new prisoners are coming. But since President Donald Trump signed an order keeping the prison open, Ring's staff is now preparing for what spokeswoman Navy Cmdr. Anne Leanos calls an "enduring mission."

"I have not been told we're getting new people. I have no order to receive new people. I've been asked some hypothetical questions about capacities and things like that, but we are not imminently expecting anybody," Ring told reporters in early June.

Guantanamo today has 40 prisoners and a staff of 1,800 troops and civilians. With the maximum-security Camp 5 prison just reopened, after a cellblock was remade into a clinic and mental health ward, the detention center can now take in another 40 men.

One wrinkle is that any new detainees are likely to be members of the Islamic State, not al-Qaida. And while some people see ISIS as offshoot of al-Qaida, the militant movements are not allies and have vastly different aims.

"Unless we got some al-Qaida from Afghanistan, which is possible, most of the conversation is about Syria, and most of those guys, I understand, are ISIS," said Ring, who doesn't decide who comes and goes from Guantanamo. "So it's possible we could get folks from either place."

Any new prisoner would be the first to arrive at Guantanamo since the CIA delivered an Afghan "high-value detainee" in March 2008. That was years before the so-called Islamic State in Iraq and Syria declared its worldwide caliphate, invaded and controlled a huge swath of Iraq and Syria and released a series of brutal videotaped killings of captives in orange jumpsuits.

Al-Qaida has "a different ideology" than ISIS, says Leanos, the prison spokeswoman. Besides, after more than a decade in military detention, there's also a "different mentality" among the captives -- who are profiled as al-Qaida members or affiliates -- and have come to understand Guantanamo prison's incentive system says the admiral's cultural adviser who is only identified with one name, Zaki. Captives who follow the guards' commands get to live communally, pray and eat in groups, take art, language and gardening classes and read more books, for example.

"If suspected ISIS fighters are transferred to Guantanamo I would expect that a legal challenge to their detention would be filed within days if not hours of their arrival," said Wells Dixon of the Center for Constitutional Rights, which has been at the forefront of representing and finding attorneys for military detainees.

He and other opponents of Guantanamo detention argue the 2001 Authorization for the Use of Military Force, Congress' permission for the president to wage war on al Qaida and the Taliban over the Sept. 11 attacks, does not apply to ISIS. "The one thing that's guaranteed is it will create years more of litigation," Dixon said.

Two possible new prisoners could be Alexanda Kotey and El Shafee Elsheikh, The Washington Post reported, who are held by U.S.-allied Kurdish militia in Iraq as suspected members of "the Beatles," a British cell blamed for the torture and killings of at least four Americans in Syria.

Defense Secretary Jim Mattis has said it is the U.S. preference to repatriate foreign fighters from allied nations. But in February, Britain stripped Kotey and Elsheikh of their citizenship, leaving the United States with three options: Let the Kurds keep them, bring them to the U.S. for federal trials, if a case could be made; or bring them to Guantanamo for possible trial by military commission, making them the first U.S. test case of the president's authority to indefinitely hold ISIS suspects without charge.

Guantanamo is not a good idea, according to the parents of slain journalists James Foley and Steven Sotloff and the two other Americans killed by ISIS, and neither is seeking a capital trial of Kotey and ElSheikh. Either move would make them "martyrs in the eyes of their fanatic, misled comrades in arms," they argued in a New York Times opinion piece in February.

President Barack Obama's administration, which saw Guantanamo prison as a recruiting symbol for al-Qaida, sought to shut it down by moving to U.S. lockups the last of the nearly 800 post-9/11 captives seized during the George W. Bush years. Congress thwarted that ambition by forbidding the transfer of Guantanamo prisoners to the United States.

But on Jan. 30, President Donald Trump revoked Obama's closure order. So the prison leadership is now making plans for 25-35 more years of detention, said Army Col. Steve Gabavics, the guard force commander.

One thought is to hire civilian Department of Defense employees for key prison staff positions -- the lawyer, spokesman, chief of staff -- on minimum two-year contracts, rather than fill those roles with revolving, temporary troops. It would be more costly to taxpayers because such hires could bring families, who live in base housing and enroll their kids in the Navy base school system.

But they could provide continuity for the Army National Guard soldiers plucked from civilian lives to serve nine-month tours of duty here, without family. Congress has already given the Army $115 million to build an 868-bed barracks for the nine-month forces.

Now the admiral is proposing to more barracks for another 960 nine-month-stay prison guards.

The troop strength recently grew by 100 soldiers and could keep growing "over the next year or so," to a combined troop and civilian staff of 2,200, Ring said. About 5,500 people live now on Guantanamo, a 45-square-mile outpost that brings in its food by air and sea and makes its own energy, desalinates its own water. A growing prison mission could grow the population past 6,000.

Nobody at the prison will say exactly where new captives might go. But the leadership makes clear that they'll be kept apart from the 40 here now, who were brought between January 2002 and March 2008 as suspected al-Qaida and Taliban members.

On a recent visit, commanders took reporters through an empty cellblock at Camp 5, the steel and cement prison that keeps one man to a cell. When captives last stayed there they could spend 22 or more hours inside their cells, let out for a short walk in ankle and wrist shackles to a shower or an outdoor recreation pen.

The recent reopening of Camp 5 also let the military bring back on line some 70 maximum-security cells with a new and improved "splash guard" on each cell door to prevent a prisoner from hurling bodily fluids on a guard.

Inside, the guards had the prison's basic issue on display -- toothbrush and paste, towel and flip-flops, two books -- illustrating what a new arrival might receive. Also, in a first, the display had a navy blue prison uniform alongside white and beige versions, a new kind of color coding for the guard force that eliminated orange for those deemed the worst behaving or most dangerous.

"ISIS, you know, have used, executed people in orange jumpsuits," said Zaki.

Plus, the admiral added, "there's a lot of photographs floating around from the early days in Camp X-Ray that maybe don't paint us in a perfect light. We strive mightily to be culturally sensitive."

This article is written by Carol Rosenberg from Miami Herald and was legally licensed via the Tribune Content Agency through the NewsCred publisher network. Please direct all licensing questions to legal@newscred.com.