A former Qaeda battlefield commander who admitted that his insurgents killed 17 U.S. and allied forces in wartime Afghanistan in the early 2000s will spend eight more years in prison under a plea agreement disclosed on Thursday.

The prisoner, Abd al-Hadi al-Iraqi, 63, has been in U.S. custody since 2006 and struck the deal two years ago. The military judge, Col. Charles L. Pritchard Jr., officially disclosed the terms at Guantánamo Bay moments after a military jury ordered Mr. Hadi to serve 30 years in prison, the maximum sentence in his war crime case.

The outcome was part of the arcane system called military commissions, which allows prisoners to reach plea deals with a senior official at the Pentagon who oversees the war court but requires the formality of a jury sentencing hearing anyway.

The jury of 11 officers rejected arguments by Mr. Hadi’s defense lawyer that the prisoner deserved leniency, if not clemency, for his early humiliations in C.I.A. custody, subsequent cooperation with U.S. investigators and failing health.

“Justice was served today,” said Bill Eggers, whose son Capt. Daniel Eggers, 28, was killed in a roadside bombing carried out by Mr. Hadi’s fighters. Mr. Eggers, who has been attending proceedings in the case since 2017, said he viewed the jury decision to give Mr. Hadi the harshest of possible sentences a just conclusion, the plea deal reduction notwithstanding.

Mr. Eggers and his daughter were among six people who testified last week about their loss in the two-week sentencing trial.

Mr. Hadi looked stoic as the sentence was announced. Unlike the jury, he was aware of the deal that reduced his sentence to 10 years, starting with his guilty plea in June 2022. He is disabled by a paralyzing spine disease and a series of surgeries at Guantánamo and sat in court in a padded therapeutic chair, listening through a headset providing Arabic translation.

The case was an unusual one at the court, which was created to prosecute terrorism cases as war crimes after the attacks of Sept. 11, 2001. While prosecutors cast Mr. Hadi as a member of the Qaeda inner circle before those attacks, there was no suggestion in his plea agreement that he knew about the plot beforehand.

Instead, he admitted to being the commander of insurgent forces who unlawfully used the cover of civilians in attacks that killed 17 U.S. and coalition forces in Afghanistan in 2003 and 2004, for example having a fighter pose as an ordinary driver in a taxi cab laden with explosives.

He also admitted to being a Qaeda liaison to the Taliban before the Sept. 11 attacks, and to providing some of his forces to help blow up monumental Buddha statues in Afghanistan’s Bamiyan Valley, a UNESCO World Heritage site, in March 2001.

The prisoner, who says his true name is Nashwan al-Tamir, was captured in Turkey in 2006 and was held incommunicado for about six months by the C.I.A. By law, he was not entitled to credit for that period, or the 15 years and eight months he had spent in U.S. detention before his 2022 guilty plea. If he were to be released, in June 2032, under the deal, he would have been held for more than 25 years as a prisoner of the United States.

But Mr. Hadi’s future is uncertain. War court prosecutors have argued that a prisoner may be held at Guantánamo even after his sentence ends as long as the war against terrorism continues. Alternatively, under the deal, the United States could transfer him to the custody of a partner nation, if one can be found that is capable of providing specialized health care and agrees to monitor his activities.

Members of his defense team, which included Army, Air Force and Marine lawyers, looked downcast as the sentence was announced.

“He expressed remorse,” said Susan Hensler, a civilian lawyer who led the team. “He understands the seriousness of what he pleaded guilty to, but he is counting on the United States to fulfill its promise of transferring him to a partner nation with a health care infrastructure to care for him.”