U.S. and British warplanes, backed by surface ships and submarines, launched a series of strikes into Houthi-controlled areas of Yemen late Monday, aimed at further degrading the capabilities of Iranian-backed Houthi militants who have sought to carry out attacks against key shipping lanes in the Middle East.

U.S. defense officials said the strikes hit multiple targets across eight locations, including an underground storage facility as well as missile launch sites and other locations linked to Houthi surveillance capabilities.

The strike locations were intentionally selected to target weapons systems not to amass casualties, a senior military official told reporters. The official assessed the underground storage facility had “more advanced conventional weaponry” in it than sites hit in the first round of strikes on Jan. 11.

“These precision strikes … are in response to a series of illegal, dangerous and destabilizing Houthi actions,” the U.S. and Britain said in a statement, noting the latest strikes were carried out with the support of Australia, Bahrain, Canada and the Netherlands.

“We will not hesitate to defend lives and the free flow of commerce in one of the world’s most critical waterways in the face of continued threats,” the statement added.

The Red Sea route carries about 15% of the world’s maritime traffic. Major shipping companies have responded to the attacks by rerouting vessels on the longer and more expensive route around Africa.

This is the eighth time U.S. military assets have struck Houthi targets in the past 10 days, but only the second time Washington has had help since Britain took part in the initial round of strikes earlier this month. A senior military official told reporters the strikes Monday had “removed significant capability” from the Houthis to launch attacks.

A U.S. defense official “directly attributed … the decline in the number and the ferocity of the [Houthi’s] maritime attacks … to the reduction in Houthi capability to carry out those attacks.”

“That does not mean they have no more capability, but we definitely believe that has had an impact,” another U.S. official said.

Since mid-November, the Houthis have launched 33 attacks on international shipping lanes, according to the Pentagon. The Houthis say their attacks are in solidarity with Palestinians in Gaza under attack from Israel.

Defense experts worry the United States is now fighting a regional war in the Middle East amid a sharp increase in attacks on American forces over the weekend.

Pentagon deputy press secretary Sabrina Singh told reporters Monday there have been 151 attacks on U.S. forces in Iraq and Syria since the October 7 Hamas terror attack against Israel, including a “barrage” of ballistic missiles fired at Ain al-Asad air base in western Iraq that constituted “a larger-scale attack than we have seen before.”

Most of the missiles were shot down, Singh said, but those that landed on the base injured one Iraqi Security Forces member and caused traumatic brain injuries in two U.S. service members.

The 151 attacks since October have injured at least 83 Americans in Iraq and Syria, a U.S. defense official said on Monday. All but two have returned to duty.

“We do not seek escalation. We don’t want to see it escalate,” Singh said Monday in response to a question from VOA.

“If you’re in a scrap with somebody and you can find a way to tie one or both of their hands behind their back, that’s not escalating. That’s de-escalating. That’s taking ability away from the other party to inflict harm,” John Kirby, National Security Council director of strategic communications, told reporters Monday at the White House.

Critics like Bradley Bowman, senior director of the Center on Military and Political Power at the Foundation for Defense of Democracies, say the U.S. military’s limited strikes against Iranian-backed targets across the Middle East amount to a “shoulder shrug” response to what he said was “absolutely” a “low-level, and in some cases not-so-low-level regional war going on.”

“Don’t expect to have good policy coming out of Washington if we can’t be objective and honest and assessing where we sit. Full points for not wanting a regional war and trying to avoid a regional war, but news flash, we appear to have one,” Bowman told VOA.

He added that as in any war, the adversary also gets a vote in whether the Middle East violence erupts into a full-blown war.

“Our adversary here is [the] Islamic Republic of Iran and its network of terror proxies, and they are repeatedly trying to kill Americans. And the only reason why we haven’t had more American casualties [is] because we’ve taken measures to defend ourselves, and we’ve gotten lucky. And sooner or later, luck runs out,” Bowman said.

Most of the attacks against U.S. forces inside Syria and Iraq have been claimed by an umbrella group calling itself the Islamic Resistance in Iraq, which has said the attacks are in retaliation for Washington’s support for Israel in the war.

Attacks by the Iran-aligned Houthi militia on ships in and around the Red Sea for the past several weeks have bogged down trade between Asia and Europe and created fears of a widening war in the Middle East. Many of the attacks by the Houthis have targeted ships that are not associated with Israel.

Also on Monday, the U.S. sanctioned Iraqi airline Fly Baghdad and its CEO Basheer Abdulkadhim Alwan al-Shabbani, saying the airline provided assistance to Iran’s military wing and its proxy groups in Iraq, Syria and Lebanon.