WASHINGTON — During six years behind bars at Guantanamo Bay, Abdul Rauf insisted he was a lowly Taliban foot soldier who delivered bread and tea to combatants, even though he was really a corps commander. He was released in 2007 and sent home to Afghanistan. Until this week, he was working as the top recruiter in Afghanistan for Islamic State militants.

Rauf, who was killed along with seven others in a U.S. drone strike Monday, and detainees like him who have returned to the battlefield are complicating President Barack Obama’s hopes of closing the detention center for terrorism suspects on the U.S. Navy base in Cuba. The administration says the prison is costly, damages America’s relationship with key allies and provides extremists a propaganda tool to woo recruits.

Obama has vowed since he was a presidential candidate to close the detention center, but members of Congress have thwarted that ambition, saying the detainees would return to the fight. They also have argued governments where the detainees would be released in the region couldn’t be expected to keep track of them and prevent them from becoming active again.

Besides Rauf, one or more of the five Taliban detainees swapped for Sgt. Bowe Bergdahl may have already been in touch with members of the al-Qaida-linked Haqqani network. Qatari officials promised to monitor the five former Taliban officials’ activities and keep them from traveling outside Qatar for a year.

White House spokesman Josh Earnest has said the five are still in Qatar, but he says efforts to keep them from working with terror organizations “have been updated” to reflect concerns about their contacts. Qatari Foreign Minister Khalid bin Mohammed al-Attiyah said at an event in Washington last week that the five continue to be closely monitored.