Monday night’s strikes, which marked the eighth round of allied attacks in 12 days, targeted an underground storage site and locations linked to the Houthis’ “missile and air surveillance capabilities,” the two countries said in a statement along with partners Australia, Bahrain, Canada, and the Netherlands. It said the strikes were meant to “disrupt and degrade” the Houthis’ capabilities.

The airstrikes were the most significant in a series of attacks since the first wave of missile and Tomahawk launches earlier this month by the US and the UK against the Houthis, which have caused chaos for shippers worldwide and disrupted traffic through a waterway that previously accounted for 12% of global trade. In the days since, the group, which receives financial backing from Iran, has vowed to step up its strikes.

Two senior US officials said the Jan. 11 and 22 strikes have significantly reduced the Houthis’ capability to mount maritime attacks, though they declined to quantify that reduction. The targets were carefully selected to strike missile and drone storage facilities while avoiding casualties and minimizing the risk of escalation, the officials said. Monday’s strikes constituted a continuation of the existing US and allied approach, they added.

The Houthi attacks — carried out to protest Israel’s bombardment of the Gaza Strip —  and the allied response have provoked fears that the US will only become further embroiled in a conflict in the Middle East and provoke a wider regional war. Earlier Monday, the US said two Navy Seals who went missing during a mission on Jan. 11 to seize Iranian weapons bound for the Houthis are now presumed dead, marking the first publicly known US military casualties linked to the conflict.

The two SEALs were part of a team that boarded a dhow near the coast of Somalia. The US forces sunk the boat after they seized components for ballistic and cruise missiles.

Last week, President Joe Biden acknowledged that the strikes so far hadn’t had the intended effect. “Are they stopping the Houthis? No. Are they going to continue? Yes,” Biden told reporters. On Sunday, Deputy National Security Advisor Jon Finer said military actions to deter the Houthis and other groups backed by Iran would take time.

“Deterrence is not a light switch,” Finer told ABC’s “This Week.” “We are taking out these stockpiles so they will not be able to conduct so many attacks over time. That will take time to play out.”

Tensions in the Middle East have steadily escalated since Hamas’s Oct. 7 assault on southern Israel that killed about 1,200 people and Israel’s counterstrikes, which have killed more than 25,000 people in the Gaza Strip, according to the Hamas-run health ministry.