The United States and Britain struck 36 Houthi targets in Yemen on Saturday in a second wave of assaults meant to further disable Iran-backed groups that have relentlessly attacked American and international interests in the wake of the Israel-Hamas war. But Washington once more did not directly target Iran as it tries to find a balance between a forceful response and intensifying the conflict.

This image provided by the U.S. Navy shows an aircraft launching from USS Dwight D. Eisenhower (CVN 69) during flight operations in the Red Sea, Jan. 22, 2024. The United States and Britain struck 36 Houthi sites in Yemen on Saturday.

The latest strikes against the Houthis were launched by U.S. warships and American and British fighter jets. The strikes follow an air assault in Iraq and Syria on Friday that targeted other Iranian-backed militias and the Iranian Revolutionary Guard in retaliation for the drone strike that killed three U.S. troops in Jordan last weekend.

The Houthi targets were in 13 different locations and were struck by U.S. F/A-18 fighter jets from the USS Dwight D. Eisenhower aircraft carrier, by British Typhoon FGR4 fighter aircraft and by the Navy destroyers USS Gravely and the USS Carney firing Tomahawk missiles from the Red Sea, according to U.S. officials and the U.K. Defense Ministry. The U.S. officials were not authorized to publicly discuss the military operation and spoke on condition of anonymity.

The U.S. warned that its response after the soldiers’ deaths at the Tower 22 base in Jordan last Sunday would not be limited to one night, one target or one group. While there has been no suggestion the Houthis were directly responsible, they have been one of the prime U.S. adversaries since Hamas attacked Israel on Oct. 7, killing more than 1,200 people and taking about 250 hostages. The Health Ministry in Hamas-ruled Gaza said that more than 26,000 people have been killed and more than 64,400 wounded in the Israeli military operation since the war began.

The Houthis have been conducting almost daily missile or drone attacks against commercial and military ships transiting the Red Sea and Gulf of Aden and they have made clear that they have no intention of scaling back their campaign despite pressure from the American and British campaign.

Mohammed al-Bukhaiti, a Houthi official, said “military operations against Israel will continue until the crimes of genocide in Gaza are stopped and the siege on its residents is lifted, no matter the sacrifices it costs us.” He wrote online that the “American-British aggression against Yemen will not go unanswered, and we will meet escalation with escalation.”

The Biden administration has indicated that this is likely not the last of its strikes. The U.S. has blamed the Jordan attack on the Islamic Resistance in Iraq, a coalition of Iranian-backed militias. Iran has tried to distance itself from the drone strike, saying the militias act independently of its direction.

Defense Secretary Lloyd Austin said in a statement that the military action, with support from Australia, Bahrain, Canada, Denmark, the Netherlands, and New Zealand, “sends a clear message to the Houthis that they will continue to bear further consequences if they do not end their illegal attacks on international shipping and naval vessels.”

He added: “We will not hesitate to defend lives and the free flow of commerce in one of the world’s most critical waterways.”

The Defense Department said the strikes targeted sites associated with the Houthis’ deeply buried weapons storage facilities, missile systems and launchers, air defense systems, radars and helicopters. The British military said it struck a ground control station west of Yemen's capital, Sanaa, that has been used to control Houthi drones that have launched against vessels in the Red Sea.

President Joe Biden was briefed on the strikes before he left Delaware on Saturday for a West Coast campaign trip, according to an administration official.

The latest strikes marked the third time the U.S. and Britain had conducted a large joint operation to strike Houthi weapon launchers, radar sites and drones. The strikes in Yemen are meant to underscore the broader message to Iran that Washington holds Tehran responsible for arming, funding and training the array of militias — from Hezbollah in Lebanon, Hamas in Gaza, the Islamic Resistance in Iraq and the Houthis in Yemen — who are behind attacks across the Mideast against U.S. and international interests.

Video shared online by people in Sanaa included the sound of explosions and at least one blast was seen lighting up the night sky. Residents described the blasts as happening around buildings associated with the Yemeni presidential compound. The Houthi-controlled state-run news agency, SABA, reported strikes in al-Bayda, Dhamar, Hajjah, Hodeida, Taiz and Sanaa provinces.

Hours before the latest joint operation, the U.S. took another self-defense strike on a site in Yemen, destroying six anti-ship cruise missiles, as it has repeatedly when it has detected a missile or drone ready to launch. The day before the strikes the U.S. destroyer Laboon and F/A-18s from the Eisenhower shot down seven drones fired from Houthi-controlled areas of Yemen into the Red Sea and the destroyer Carney shot down a drone fired in the Gulf of Aden and U.S. forces took out four more drones that were prepared to launch.

The Houthis’ attacks have led shipping companies to reroute their vessels from the Red Sea, sending them around Africa through the Cape of Good Hope — a much longer, costlier and less efficient passage. The threats also have led the U.S. and its allies to set up a joint mission where warships from participating nations provide a protective umbrella of air defense for ships as they travel the critical waterway that runs from the Suez Canal down to the Bab el-Mandeb Strait.

During normal operations about 400 commercial vessels transit the southern Red Sea at any given time.

In the wake of the strikes Friday in Iraq and Syria, Hussein al-Mosawi, spokesperson for Harakat al-Nujaba, one of the main Iranian-backed militias in Iraq, said Washington “must understand that every action elicits a reaction.” But in an AP interview in Baghdad, he also struck a more conciliatory tone. "We do not wish to escalate or widen regional tensions,” he said.

Iraqi officials have attempted to rein in the militias, while also condemning U.S. retaliatory strikes as a violation of Iraqi sovereignty and calling for an exit of the 2,500 U.S. troops who are in the country as part of an international coalition to fight the Islamic State group. Last month, Iraqi and U.S. military officials launched formal talks to wind down the coalition’s presence, a process that will likely take years.

What to know about wave of deadly US strikes in Middle East

In the past 24 hours, the U.S. military has hit more than 100 targets across Iraq, Syria and Yemen, striking Iranian-backed proxies that have ramped up their own attacks on U.S. troops in the region since October.

Washington began late Friday with major airstrikes on more than 85 targets across seven locations in Iraq and Syria, a response to a drone strike in Jordan that killed three American soldiers on Sunday.

Then on Saturday, the U.S. military struck 36 targets at 13 locations in areas of Yemen controlled by Houthi rebels, a separate move in connection to the militant group’s ongoing attacks on commercial and U.S. naval vessels in the Red Sea.

The intense targeting of the Iranian-backed groups has been met with criticism in the U.S., with some lawmakers arguing the Biden administration’s response is too little too late and others saying it’s not enough.

The move has also roiled an already volatile situation in the Middle East, where the Iranian-proxy groups claim they are targeting U.S. forces in response to the Israeli war against Palestinian militant group Hamas in Gaza, which began in October.

Here’s what to know about the strikes:

Targets

U.S. Central Command (CENTCOM), the arm of the U.S. military that oversees forces in the Middle East, began airstrikes Friday evening in Iraq and Syria against Iran’s Islamic Revolutionary Guards Corps (IRGC) Quds Force “and affiliated militia groups.”

U.S. forces struck more than 85 targets at seven locations — four in Syria and three in Iraq — using various war planes, including B-1 long-range bombers flown from the United States, dropping more than 125 precision munitions, according to CENTCOM.

The strikes also reportedly targeted the headquarters of the Popular Mobilization Forces, a coalition of Iraqi militia groups that includes Iranian-backed militants that provide official security in Baghdad, according to Iranian Telegram channels.

Areas struck included command and control centers, intelligence facilities and weapons storage facilities used by the Iran-backed militias to attack U.S. and coalition forces, the Pentagon later said in a statement.

The Biden administration has said the strikes are the first in a series of actions by Washington to respond to the attack in Jordan — which it has blamed on the Islamic Resistance in Iraq, an umbrella group of militias backed by Tehran. The actions are intended to wipe out capabilities used to target American troops as well as send a message to ward off further attacks, officials say.

“The goal here is to get these attacks to stop. We’re not looking for a war with Iran,” White House national security spokesperson John Kirby told reporters Friday.

Separately, on Saturday the U.S. and the United Kingdom hit 36 Houthi targets at 13 locations in Yemen using ships and aircraft, focusing on facilities and equipment used to attack international merchant vessels and U.S. Navy ships in the Red Sea, Bab Al-Mandeb Strait, and the Gulf of Aden, according to the Pentagon.

This is the third set of strikes carried out by the U.S. in Yemen as part of a coalition that also includes the United Kingdom, Australia, Bahrain, Canada, Denmark, the Netherlands and New Zealand.

The targets included multiple underground storage facilities, command and control, missile systems, UAV storage and operations sites, radars, and helicopters, the Defense Department said.

The U.S. military also continues to hit Houthi cruise missiles in Yemen poised to be launched into the Red Sea, knocking out six on Saturday alone. Washington officials say these strikes are defensive in nature.

Timeline

The strikes come less than a week after three Army reservists were killed and some 40 were injured when a suicide drone hit Tower 22, a U.S. base in Jordan near the Syria border on Jan. 28.

The next day, President Biden met with members of his national security team, including national security adviser Jake Sullivan and Defense Secretary Lloyd Austin.

Shortly thereafter, on Jan. 30, Biden announced he had decided how he planned to respond to the attack.

More strikes are expected in the coming days, with Austin on Friday stating: “This is the start of our response.”

Since Oct. 7, U.S. troops have been attacked over 160 times in Iraq, Syria and Jordan with a mix of rockets and one-way attack drones.

Deaths

While the U.S. has not come out with a tally of casulties in the wake of the strikes in Iraq and Syria, Baghdad’s government has accused Washington of killing 16 people, including civilians, and wounded 25.

In Syria, meanwhile, the strikes reportedly killed 23 people who had been guarding the targeted locations, according to Rami Abdulrahman, director of the Syrian Observatory for Human Rights, as reported by Reuters.

There is also no official U.S. tally of any casualties from the strikes in Yemen.

Joint Staff Director Lt. Gen. Douglas Sims, who spoke to reporters Friday, said the strikes were carried out with the knowledge that those in the facilities would likely be killed.

Response

Biden’s decision to authorize the strikes has been met with sharp criticisms on the right, with several GOP lawmakers insisting the commander-in-chief was too slow in his response or had not gone far enough.

“The tragic deaths of three U.S. troops in Jordan, perpetrated by Iran-backed militias, demanded a clear and forceful response. Unfortunately, the administration waited for a week and telegraphed to the world, including to Iran, the nature of our response,” House Speaker Mike Johnson (R-La.) said in a statement.

And Senate Armed Services Committee ranking member Roger Wicker (R-Miss.) said the airstrikes are “welcome,” but “too late” for those who died.

Other Republicans, including former national security adviser John Bolton, called for Biden to authorize strikes in Iran directly, so it can “send a message.”

That route is unlikely considering that any move hitting Iranian soil could provoke an all-out war between Washington and Tehran, something Biden has repeatedly said he does not want.

The strikes in Iraq are also expected to further intensify ongoing discussions between Baghdad and Washington over the future of the American military presence in the country, where some 2,500 troops are based to train and assist Iraq in the fight against Islamic State extremist group.

Iraqi officials complain their country is being turned back into a warzone as the U.S. and Iranian groups clash, with a government spokesperson on Saturday accusing the U.S. of violating international law and lying about the circumstances surrounding its retaliatory strikes.

U.S. officials said they informed the Iraqi government prior to carrying out the strikes, but Bassem Al-Awadi claims that Washington “deliberately deceived and falsified the facts, by announcing prior coordination to commit this aggression, which is a false claim aimed at misleading international public opinion and disavowing legal responsibility for this rejected crime in accordance with all international laws.”

In Iran, meanwhile, groups quickly condemned the U.S. for the attack with Iranian President Ebrahim Raisi warning in a Friday address that Tehran would respond.

“We have often clarified that Iran will not initiate a war but will answer bullies firmly and authoritatively,” Raisi said, according to state-run news outlet Islamic Republic News Agency (IRNA).

And Iran’s foreign minister Hossein Amir-Abdollahian on Saturday said the move worsens the chance of reaching a political solution in the Middle East.

The U.S. decision has “complicated the situation and made it more difficult to reach a political solution,” Amir-Abdollahian told the United Nations’ special envoy for Yemen while meeting in Tehran, according to IRNA.

He added that the U.S. strikes were a “continuation of Washington’s wrong and failed approach to resolve issues by force and through militarism.”

The United Nations Security Council is also expected to meet on Monday to discuss the U.S. strikes in Iraq and Syria, CNN reported.