After U.S.-Led Strikes in Yemen, How Wide Will the Middle East War Get?

From the outbreak of the Israeli-Hamas war nearly 100 days ago, President Biden and his aides have struggled to keep the war contained, fearful that a regional escalation could quickly draw in American forces.

Now, with the American-led strike on nearly 30 sites in Yemen on Thursday and a smaller strike the next day, there is no longer a question of whether there will be a regional conflict. It has already begun. The biggest questions now are the conflict’s intensity and whether it can be contained.

This is exactly the outcome no one wanted, presumably including Iran.

“We’re not interested in a war with Yemen. We’re not interested in a conflict of any kind,” John F. Kirby, a White House spokesman, said on Friday. “In fact, everything the president has been doing has been trying to prevent any escalation of conflict, including the strikes last night.”

Mr. Biden’s decision to unleash airstrikes, after resisting calls to act against the Yemen-based Houthi militants whose repeated attacks on shipping in the Red Sea were beginning to take a toll on global commerce, is a clear shift in strategy. After issuing a series of warnings, officials said, Mr. Biden felt his hand was forced after a barrage of missile and drone attacks on Tuesday were directed at an American cargo ship and the Navy vessels around it.

“This is already a regional war, no longer limited to Gaza, but already spread to Lebanon, Iraq, Syria and Yemen,” said Hugh Lovatt, a Mideast expert for the European Council on Foreign Relations. Washington, he added, wanted to demonstrate that it was ready to deter Iranian provocations, so it conspicuously placed its aircraft carriers and fighters in position to respond quickly. But those same positions leave the United States more exposed.

Over the course of 12 weeks, attacks on Israeli, American and Western interests have come from Lebanon, Iraq and Syria, prompting modest, carefully targeted responses from American and Israeli forces. The United States also issued warnings to Iran, which the Americans say is acting as a loose coordinator.

What was notable about the retaliatory strike in Yemen was its breadth: Employing fighter jets and sea-launched missiles, U.S. and British forces, backed up by a small number of other allies, hit a wide number of Houthi missile and drone sites.

Mr. Biden is walking the fine line between deterrence and escalation, and his aides concede there is no science to the calculation. Tehran and its allies, including Hezbollah in Lebanon, have been careful in their support for Hamas, keeping their actions within limits, to prevent a larger American military response that could threaten Tehran’s exercise of power in Lebanon, Iraq and Syria.

But how much control Iran has over its proxies is in question, and its leaders may also be misreading American and Israeli red lines.

The Houthis, a small Iranian-backed tribe in Yemen, have been among the most aggressive in pushing the envelope, trying to block international trading routes through the Red Sea and ignoring American and Western warnings to desist.

Houthi officials say that the sole goal of their attacks is to force Israel to halt its military campaign and to allow the free flow of aid into Gaza.

Western diplomats said that there had been reluctance to strike back at the Houthis, in part to avoid upending a truce in the Yemeni civil war, and in part because of the difficulty of eliminating their threat entirely. But the Houthis’ repeated attacks on ships, their direct fire on American helicopters, and their attack Tuesday on an American cargo vessel, left the United States with what officials said was no real choice.

U.S. officials said the Pentagon carried out a second round of strikes on Friday against the Houthis, bombing a radar facility in Yemen.

It is not known how long it will take the Houthis to recover and threaten ships in the Red Sea again, as they have vowed. So far the response has been muted, with just a single anti-ship missile lobbed harmlessly into the Red Sea, far from any passing vessel, a Pentagon official told reporters earlier on Friday.

But deeper American military involvement also adds to the perception in the larger world that the United States is acting even more directly on behalf of Israel, risking further damage to American and Western standing as the death toll rises in Gaza. Israel now is defending its conduct against the charge of genocide in an international court.

Iran is using proxies like Hezbollah and the Houthis to distance itself from their actions and maintain its credibility in the region, attempting to avoid a direct attack, which could put at risk the Islamic Revolution and its nuclear program.

But Iran is also being pulled along by those very proxies.

“Iran is really pushing it,” said François Heisbourg, a French military analyst. “It’s another reason they don’t want a war now: They want their centrifuges to run peacefully.” The Iranians do not have a nuclear weapon, but could enrich enough uranium to weapons grade in a few weeks, from the current 60 percent enrichment to 90 percent, he said. “They’ve done 95 percent of the work.”

Israel also is ratcheting up its attacks on Iran’s proxies, especially in Lebanon and Syria. After the attack by Hamas, Hezbollah in Lebanon began a series of strikes from Lebanon, leading Israel to evacuate citizens near the conflict.

Following that, Israel’s air campaign has killed 19 Hezbollah members in Syria in three months, more than twice the rest of 2023 combined, according to a count by Reuters news agency. More than 130 Hezbollah fighters have also been killed by Israel in Lebanon in the same period.

Amine Hoteit, a retired Lebanese army general and analyst, listed several goals of the Israeli attacks in Syria: to keep attention there and to press the Syrian government “to cut off the Iranian supply route.”

U.S. troops deployed to Iraq and Syria to prevent a resurgence of ISIS have come under attack from Iran-backed militias 130 times since Oct. 17, according to the Pentagon’s tally on Thursday, totaling 53 attacks in Iraq and 77 in Syria. The United States has retaliated on fewer than 10 occasions, usually after American casualties.

Each time, the United States has said its response is meant to deter further attacks and is aimed at sending a message to Iran and its proxies, who operate freely in Iraq and Syria. But no American troops have been killed. The worry, according to U.S. officials, is that sooner or later, one of the attacks will kill troops, and then the response would be much more deadly and could spiral out of control.

On Jan. 4, the U.S. military launched a rare retaliatory strike in Baghdad that killed a militia leader it blames for recent attacks on U.S. personnel, a move condemned by Iraq’s government.

While the Iraqi government is now dominated by parties close to Iran, the American presence has been tolerated largely because of the fear that without U.S. help, the Islamic State could quickly regain ground.

But on Friday, Iraq’s foreign ministry condemned the strikes on the Houthis in Yemen. “We believe that expanding the scope of targets does not represent a solution to the problem — rather, it will lead to an expansion of the scope of the war,” the statement said.

While the main attention has been on Hamas in Gaza and Hezbollah, the Houthi threat to trade has the potential for the largest global impact, since some 30 percent of the world’s container ships pass through the Red Sea. Already Volvo, Tesla and other carmakers in Europe have suspended production for a few days or more because of interruptions in receiving parts as ships route around the Red Sea and Suez Canal.

The United States and more than a dozen other countries have created a coalition to protect shipping, Operation Prosperity Guardian. But the Houthis have continued to try to attack ships, with Israeli connections or not, and Maersk decided to pause all Red Sea shipping after a Dec. 31 attack on one of its ships. It has warned its customers to expect significant disruptions and analysts expect higher prices to add to global inflation.

In public speeches this week, lran’s supreme leader Ayatollah Ali Khamenei and Hezbollah leader Sheikh Hassan Nasrallah reiterated that they do not want an enlarged war. But Colin P. Clarke, a counterterrorism expert who is the director of research at the Soufan Group, said Israel could not afford to be complacent given its grave miscalculation before Oct. 7 that Hamas was also not interested in a war.

Recent assassinations that struck at the heart of Iran’s ties to Hezbollah and Hamas have unnerved Iranians who have described them in chat rooms and social media as being “slapped over and over.”

Brig. Gen. Sayyed Razi Mousavi, killed on Christmas in Damascus, for two decades had been in charge of procuring missiles, rockets and drones for Hezbollah in Lebanon and allied militia groups in Syria and Iraq, according to Iranian media reports. Mr. Khamenei performed the prayer of the dead ritual above his body at his funeral, an honor reserved for the most revered underlings.

Saleh al-Arouri, deputy political head of Hamas, killed in a drone strike in the heart of Hezbollah’s power base in Dahieh district of Beirut, was the closest member of Hamas to Iran and Hezbollah and the person they trusted most with sensitive messaging and facilitating funding and technical know-how from Iran.

Alissa J. Rubin contributed reporting from Baghdad, Hwaida Saad from Beirut, and Helene Cooper and Eric Schmitt from Washington.