It hardly seems a fair fight: a ragtag rebel movement in one of the world’s poorest countries, already locked in a draining civil war at home, taking on the world’s strongest military power and its allies, determined to protect a waterway critical to global commerce.

Months into the clash, however, Yemen’s Houthis are showing no signs of going away.

The Iran-backed movement now has launched almost 200 attacks against military and commercial ships passing through the Red Sea since November 2023. The U.S. and Great Britain have responded with multiple retaliatory air strikes deep into Yemen and have spent more than six months downing swarms of Houthi drones and rockets heading toward merchant vessels at sea.

But despite the massive U.S. and international naval coalition arrayed against them, the Houthis — formally known as Ansar Allah — are continuing their barrage and succeeding in creating a vast disruption in international shipping patterns. The U.S. and its allies have launched some 450 strikes against Houthi positions along the Yemeni coastline, including some of the most intensive sorties just in the past few weeks, in a campaign that some are comparing to the arcade game Whac-a-Mole.

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“The Houthis have suffered some losses, but they retain the ability to obstruct maritime shipping in the Red Sea,” Thomas Juneau, associate professor who focuses on the Middle East at the University of Ottawa’s Graduate School of Public and International Affairs, recently told the website Responsible Statecraft. “And perhaps more importantly, beyond the material damage they have suffered, their intent to continue obstructing shipping in the Red Sea has not wavered.”

As recently as last week, Houthi rebels, who say they are acting in solidarity with Palestinian militants battling Israeli forces in Gaza, launched strikes against two commercial ships, the M/V Tutor and the M/V Verbena.

On June 12, they attacked the Liberian-flagged and Greek-owned Tutor with an uncrewed surface vessel that resulted in severe flooding and damage to the engine room. One of the civilian mariners aboard remains missing following the strike. The crew abandoned the ship and were rescued by the U.S.S. Philippine Sea and other vessels, U.S. officials said.

The Houthis struck again the next day, launching two separate missile attacks on June 13 at the Verbena, which sails under the flag of Palau and is owned by Ukrainians. One of the crew members had to be medically evacuated, officials said.

After two days of trying to bring the fires under control, the Verbena crew also was forced to abandon the ship. U.S. officials said the Iranian naval frigate Jamaran was only eight nautical miles away but refused to respond to the crew’s distress call.

The frustration in Washington and in the region is palpable and growing.

“The continued malign and reckless behavior by the Iranian-backed Houthis threatens regional stability and endangers the lives of mariners across the Red Sea and the Gulf of Aden,” U.S. Central Command officials said in a statement. “The Houthis claim to be acting on behalf of the Palestinians in Gaza and yet they are targeting and threatening the lives of third-country nationals who have nothing to do with the conflict in Gaza.”

In early December 2023, the Houthis threatened to attack any ship they believed was heading to Israeli ports. But, most of the strikes before and since have been against civilian ships with Israeli affiliations that were tenuous at best. The Yemeni group quickly expanded their target list, saying any ship affiliated with the U.S. or its allies also could face attacks, the Defense Intelligence Agency said in a recent report.

The Houthis use of a drone uncrewed surface vessel (USV) against the M/V Tutor is a sign the nature of their attacks on Red Sea merchant shipping might be evolving, said Bradley Bowman, senior director of the Center on Military and Political Power at the Foundation for Defense of Democracies think tank in Washington.

“We should expect to see more unmanned surface vessel attacks. [They] are being used by Ukraine in the Black Sea to counter Russian aggression and they are being used by Iran-backed terror organizations in the Red Sea to threaten commercial vessels,” Mr. Bowman said Tuesday. “The U.S. has continued to destroy Houthi offensive capabilities in Yemen, but the terror group continues to have sufficient means to threaten shipping.”

The fact that the Houthis can continue launching effective strikes against ship traffic in the Red Sea suggests they continue to enjoy a steady supply of armaments from their allies in Tehran, Mr. Bowman said.

“An effort to destroy capabilities in Yemen that does not devote sufficient attention and resources to interdicting weapons shipments from Iran to Yemen is not unlike the homeowner cleaning up puddles but ignoring the hole in the roof,” he said.

Shipping shifts

Container shipping through the Red Sea typically accounts for 10-15% of international maritime trade but it has declined by about 90% since December 2023. Alternate shipping routes around Africa add about 11,000 nautical miles, up to two weeks of extra transit time and about $1 million in fuel costs for each voyage, according to the Defense Intelligence Agency.

At least 20 major energy and shipping companies have altered their routes to avoid Houthi attacks. Taking the long route around Africa can be less expensive because shippers don’t have to factor in the combined costs of crew bonuses, risk insurance now running 1,000% greater than before, and the $400,000 to $700,000 fees to transit the Suez Canal, DIA officials said.

Deputy Pentagon spokesperson Sabrina Singh said the U.S. Navy’s role in the region is to maintain freedom of navigation and uphold international law and defended the U.S. campaign so far. She said American forces have been “pretty successful” so far.

“We certainly understand the global impact and the effect on global commerce if shipping routes have to be re-routed,” Ms. Singh said Monday. “It’s up to the shipping companies to decide if they want to continue transiting through the Red Sea. That’s a decision that each company has to make.”

Officials with the International Maritime Organization, a specialized UN agency for regulating marine transportation, said they were appalled by the latest Houthi attacks in the Red Sea and called for increased international assistance for seafarers.

“I strongly condemn any type of attack against international shipping, regardless of its motivation or cause,” IMO Secretary-General Arsenio Dominguez said Tuesday in a statement. “This situation cannot go on. Everybody is going to feel the negative effect if international shipping is not able to trade as normal. But our commitment is, above all, safeguarding the safety of all seafarers.”