The tit-for-tat raises questions about whether groups backed by Iran can be deterred after a flurry of attacks targeting American troops.
Just hours after U.S. fighter jets bombed facilities used by Iran’s Islamic Revolutionary Guards Corps and its proxies in Syria early Friday, the proxies fired back — launching an attack drone at U.S. forces in western Iraq.
American air defenses shot down the drone a few miles from Al Asad Air Base, causing no injuries or damage on the ground, U.S. officials said on Friday. Pentagon officials also said that rockets were fired into northern Syria on Friday but landed far from American troops.
Pentagon officials have attributed the attacks to Iran-backed militias.
But the tit-for-tat raised questions about whether the airstrikes that were carried out after a flurry of rocket and drone attacks against U.S. forces in Iraq and Syria can achieve one of their major goals: to deter further attacks.
“The United States does not seek conflict and has no intention nor desire to engage in further hostilities, but these Iranian-backed attacks against U.S. forces are unacceptable and must stop,” Defense Secretary Lloyd J. Austin III said in a statement after what he described as “self-defense” strikes.
The airstrikes conducted by two Air Force F-16s and one F-15 were calibrated to send a strong message to Iran but not so strong as to escalate the hostilities, U.S. officials said. The targets were arms and ammunition storage buildings that supplied the Iran-backed militias involved in the recent attacks against Americans, Pentagon officials said.
“This was our way of saying ‘cut it out,’ but no more than that,” said Charles Lister of the Middle East Institute in Washington. “The Iranians won’t be deterred, of course, so this will likely prove to be the first step in several attempts to reinforce deterrence.”
Since Hamas’s surprise attack against Israel on Oct. 7, President Biden and his aides have sought to prevent the war between Israel and Hamas from spilling over into a regional conflict with Iran and its proxies in Lebanon, Syria and Iraq. The Pentagon has rushed two aircraft carriers and dozens of extra warplanes to the region to make this point.
But with the near daily attacks against U.S. forces over the past 10 days — the Pentagon’s tally climbed to at least 20 by late Friday — pressure had been mounting for a military response.
Republican critics and some air power advocates said on Friday that the U.S. retaliatory strikes were important but not enough to deter Iran and its proxies.
“They demonstrate that we won’t just take incoming attacks without a response, but they were not, and are not, sufficient to deter additional future attacks,” said David A. Deptula, a retired three-star Air Force general and the dean of the Mitchell Institute for Aerospace Studies.
Senator Tom Cotton, Republican of Arkansas and a member of the Armed Services Committee, said the U.S. retaliation, especially on unoccupied proxy warehouses, “merely validates Iran’s strategy to use proxies to attack Americans.”
“They are laughing at us in Tehran,” he added.
Biden administration officials say a similar spate of attacks involving Iran-backed militias and retaliatory American airstrikes in March eventually led to an uneasy six-month hiatus of rocket and drone attacks against U.S. forces in Iraq and Syria until the recent strikes.
A U.S. official said on Friday that the Biden administration did not believe that the Iranian government wanted a war with the United States. Iran, the official said, is believed to be wary of the Shiite militias taking the attacks so far that they drag Washington and Tehran into direct conflict.
At the same time, the official said that Tehran wanted to give the militias space to express their anger.
But Karim Sadjadpour, an Iran expert with the Carnegie Endowment for International Peace, warned that Iran knows the Biden administration has little appetite for another war in the region. Officials in Tehran could miscalculate and think that they have more leeway to harass the United States because they do not believe President Biden wants a war.
“The U.S. dilemma is that after two decades of failure in the Middle East, there’s little popular support for greater U.S. military involvement in the region,” Mr. Sadjadpour said. “The Islamic republic knows that, which makes deterring Iranian aggression more challenging.”
The predawn U.S. retaliatory strikes on Friday came just hours after the Pentagon announced that 19 U.S. military members based at Al Asad in Iraq and the al-Tanf garrison in Syria had suffered traumatic brain injuries after rocket and drone attacks from Iran-backed militants last week.
There are 2,500 U.S. troops in Iraq and 900 in Syria, mainly helping local allies conduct counterterrorism missions against the Islamic State.
In 2016, the American military turned al-Tanf into a small outpost. It is on the Baghdad-Damascus highway — a vital link for forces backed by Iran, Syria’s ally, in a corridor that runs from Tehran, through Iraq and Syria to southern Lebanon.
In October 2021, Iran ordered an armed drone strike on al-Tanf in retaliation for Israeli airstrikes against Iranian forces in Syria, American and Israeli officials said, an escalation of Iran’s shadow war with Israel that created new dangers for U.S. forces in the Middle East.
Pentagon officials said they were still assessing the damage from the strikes on Friday to gauge their success. The two Air Force F-16s and the F-15, accompanied by MQ-9 drones, dropped more than 20 precision-guided bombs on a weapons storage facility and an ammunition storage facility near al-Bukamal, Syria, officials said.
Mr. Lister said the Revolutionary Guards Corps and its proxies used the area around al-Bukamal to move their forces, weapons and other supplies between Iraq and eastern Syria.