BAGHDAD — An American soldier was killed in action in Iraq for the first time since the renewed military intervention here last year, during a Kurdish and U.S. commando raid to free prisoners being held by Islamic State militants on Thursday, the Pentagon said.
The raid, near the northern town of Hawija, freed about 70 prisoners but not the group the soldiers had expected to find, U.S. and Iraqi officials said. U.S. officials said that five Islamic State fighters had been detained and that important intelligence about the terrorist group had been recovered.
The raid was the first time U.S. soldiers had been confirmed to be directly accompanying local forces in Iraq onto the battlefield against the Islamic State since President Barack Obama sent troops back to the country last year. Until now, the U.S. contingent, which numbers around 3,500, had been limited to training and advising the Iraqi and Kurdish forces on military bases and training areas. But senior U.S. military officials have long signaled that they might ask the White House for permission to send small teams into the field with Iraqi forces for some important operations, such as the battle for Mosul.
The Pentagon press secretary, Peter Cook, said the United States was trying to help a loyal ally — the Kurdish Regional Government — and was also rushing to save lives.
"This was a unique circumstance in which very close partners of the United States made a specific request for our assistance," he said. "So I would not suggest that this is something that's going to now happen on a regular basis."
It was not, Cook insisted, a forerunner of a more aggressive posture in which U.S. troops would regularly join the Iraqis on combat operations.
The decision to use U.S. helicopters to fly Kurdish commandos to Hawija, and to have U.S. special operations forces join them in a supporting role, was taken by Defense Secretary Ash Carter. The White House, Cook said, was informed in advance.
Providing new details about the operation, U.S. officials said Thursday night that it had been mounted at the request of the Kurdish officials who insisted they had solid intelligence that the Islamic State was about to massacre prisoners, including a number of peshmerga fighters, as the Kurdish forces are known.
"They were going with or without us," said a senior Defense Department official who spoke on the condition of anonymity to discuss a classified operation. "We wanted to stand behind an important ally."
Fears that the prisoners were in danger may have been reinforced by the militants' actions in recent days. An Iraqi in the Hawija area, who asked not to be named because he feared retribution from the Islamic State, said this week that the militants had recently executed 11 young men who were the sons or relatives of police officers or other Iraqi forces. He said their bodies had been displayed on a nearby bridge.
Five U.S. helicopters were involved in the raid, a mix of Chinook and Black Hawk choppers. The U.S. forces included commandos from the Delta Force counterterrorism unit, officials said.
As the operation began, the United States conducted an airstrike to destroy a bridge near Hawija and hamper the Islamic State's ability to send reinforcements. But the operation soon became an intense firefight.
Kurdish forces were to take the lead in the operation while U.S. soldiers, who were to play a supporting role, initially were near a wall that was some distance from the objective, officials said.
But the Kurds were pinned down by fire from the militants. So the Americans began to maneuver to relieve the pressure on their Kurdish allies and one of them was fatally wounded, said Col. Steven H. Warren, a spokesman for the U.S.-led coalition in Iraq.
When the prisoners were freed, the Kurds were surprised to see that no peshmerga fighters were among them. It is not clear whether the initial intelligence was bad or the Islamic State had moved the Kurds somewhere else.
Instead of the about 20 prisoners the commandos had anticipated, there were 69, the Kurds said. They included more than 20 Iraqi security forces, some local residents and apparently some militants whom the Islamic State suspected as being traitors, according to U.S. officials.
Freed hostages have told Iraqi and U.S. officials in Erbil, where they were taken, that they had been told they were to be executed at dawn Thursday after the morning prayer. Trench graves had already been dug.
As the U.S. helicopters flew away, an American F-15 jet bombed the house that the Islamic State has used as its prison. Iraqis from the area said the building that the militants took over was owned by a local judge who had left the region.
"They cut off roads and raided the place successfully," Najmaldin Karim, the governor of the surrounding Kirkuk province, said in a telephone interview. "They were able to take people with them."
Kurdish security officials said Thursday night in a statement that more than 20 militants had been killed in the firefight and that six militants, not the five reported by the United States, had been captured. The Kurdish statement said that three Kurdish commandos had been injured.
A news agency linked with the Islamic State asserted that three militants who were defending the prison had been killed, and it said that Islamic State fighters had killed some of their prisoners.
The operation comes as Iraq and the U.S.-led coalition have been trying to regain the initiative, stepping up the pressure against the militants in Ramadi, Beiji and other areas in Iraq, as well as in Syria.
Hawija is under the control of the Islamic State and has been an important flash point. Kurdish forces advanced toward the area in recent weeks and were said to have taken significant casualties, according to U.S. officials.
The raid may intensify the public debate in the United States over the U.S. military role in the region. The Obama administration has said that its goal is to degrade and ultimately defeat the Islamic State, but the campaign against the militants has progressed slowly.
Some experts say there is no such thing as a risk-free conflict and that U.S. teams will need to venture outside their bases to advise Iraqi forces if they are to evict the Islamic State from Iraq. Critics, however, are likely to portray the raid as a case of mission creep.
The Pentagon has not yet named the soldier who was killed, a standard procedure until relatives are notified.
Military personnel from other coalition nations have also been killed in the campaign against the Islamic State since its advance through Iraq last year. A Canadian soldier was killed in northern Iraq in March in a so-called friendly-fire incident involving Kurdish troops. And a Jordanian pilot was burned to death this year by the Islamic State after his plane crashed in Syria in December.
While American commando operations have taken place in Syria, none had previously been confirmed to have happened in Iraq. In May, special operations commandos swooped in on a top ISIS financier, Abu Sayyaf, in eastern Syria, killing him and capturing a trove of computers, according to U.S. officials.