“These narrowly tailored strikes in self-defense were intended solely to protect and defend U.S. personnel in Iraq and Syria,” Mr. Austin said. “They are separate and distinct from the ongoing conflict between Israel and Hamas, and do not constitute a shift in our approach to the Israel-Hamas conflict.”
He added: “If attacks by Iran’s proxies against U.S. forces continue, we will not hesitate to take further necessary measures to protect our people.”
A senior Defense Department official told reporters in a briefing late Thursday that the airstrikes were not coordinated with Israel’s military.
Pentagon officials offered few details about the strikes themselves, how much damage they caused and what kind of response they might draw from Iran and its allies. They gave the following account:
Two Air Force F-16 strike aircraft based in the region, accompanied by MQ-9 drones, dropped more than 30 precision-guided bombs on a weapons storage facility and an ammunition storage facility near Abu Kamal, Syria. While rockets or drones had not been launched from the site, officials said munitions stored at the facilities were used in the recent attacks against U.S. forces.
Pentagon officials said there were people at the site during the day on Thursday, but it was unclear whether any Iranian or militia personnel were injured or killed in the strikes.
As in the past, the United States opted to strike Iran-backed targets based in eastern Syria, not southern Iraq, where the groups operate with wide latitude. Administration officials have urged Iraqi officials to crack down on the groups in that area with little success. Still, conducting American airstrikes could have a destabilizing effect on the Iraqi government, which works closely with the U.S. government.
“The U.S. sent a message tonight,” Mick Mulroy, a former defense official and retired C.I.A. officer, said in a statement late Thursday. “We will directly respond against Iran, and specifically the I.R.G.C., if they continue to attack our military positions and personnel in Iraq and Syria.”
Mr. Biden, asked on Wednesday about drone strikes against U.S. military personnel in Iraq and Syria in recent days, said he had warned Iran “that if they continue to move against those troops, we will respond.”
The predawn U.S. retaliatory strikes on Friday came just hours after the Pentagon announced that 19 U.S. military members based in Iraq and Syria had suffered traumatic brain injuries after rocket and drone attacks from Iran-backed militants last week.
The Defense Department had previously said that 21 service members had suffered minor injuries but returned to duty after the attacks on Oct. 17 and 18 at Al Asad Air Base in western Iraq and al-Tanf garrison in southern Syria.