The U.S. is mustering an international armada to deter Iranian-backed Houthi militias from Yemen from attacking shipping in the Red Sea, one of the world’s most important waterways for global trade, including energy cargos.

The Houthis’ drone and missile attacks are ostensibly a response to the war between Israel and Hamas, but fears are growing that the broader world economy could be disrupted as commercial vessels are forced to reroute.

On Tuesday, U.S. Secretary of Defense Lloyd Austin held a videoconference with 43 countries, the EU and NATO, telling them that “attacks had already impacted the global economy and would continue to threaten commercial shipping if the international community did not come together to address the issue collectively.”

Earlier this week, the U.S. announced an international security effort dubbed Operation Prosperity Guardian that listed the U.K., Bahrain, Canada, France, Italy, the Netherlands, Norway, the Seychelles and Spain as participants. Madrid, however, said it wouldn’t take part. 

The Houthis were quick to respond. 

“Even if America succeeds in mobilizing the entire world, our military operations will not stop unless the genocide crimes in Gaza stop and allow food, medicine, and fuel to enter its besieged population, no matter the sacrifices it costs us,” said Mohammed Al-Bukaiti, a member of the Ansar Allah political bureau, in a post on X. 

Here’s what you need to know about the Red Sea crisis.

1. Who are the Houthis and why are they attacking ships?

International observers have put the blame for the hijackings, missiles and drone attacks on Houthi rebels in Yemen, who have stepped up their attacks since the Israel-Hamas war started. The Shi’ite Islamist group is part of the so-called “axis of resistance” against Israel and is armed by Tehran. Almost certainly due to Iranian support with ballistics, the Houthis have directly targeted Israel since the beginning of the war, firing missiles and drones up the Red Sea toward the resort of Eilat.

The Houthis have been embroiled in Yemen’s long-running civil war and have been locked in combat with an intervention force in the country led by Sunni Saudi Arabia. The Houthis have claimed several major strikes against high-value energy installations in Saudi Arabia over the past years, but many international observers have identified some of their bigger claims as implausible, seeing the Houthis as a smokescreen for direct Iranian action against its arch enemy Riyadh.

After first firing drones and cruise missiles at Israel, the rebels are now targeting commercial vessels it deems linked to Israel. The Houthis have launched about 100 drone and ballistic missile attacks against 10 commercial vessels, the U.S. Department of Defense said on Tuesday. 

As a result, some of the world’s largest shipping companies, including Italian-Swiss MSC, Danish giant Maersk and France’s CMA CGM, were forced to reroute to avoid being targeted. BP also paused shipping through the Red Sea. 

2. Why is the Red Sea so important?

The Bab el-Mandeb (Gate of Lamentation) strait between Djibouti and Yemen where the Houthis have been attacking vessels marks the southern entrance to the Red Sea, which connects to the Suez Canal and is a crucial link between Europe and Asia. 

Estimate are that 12 to 15 percent passes of global trade takes this route, representing 30 percent of global container traffic. Some 7 percent to 10 percent of the world’s oil and 8 percent of liquefied natural gas are also shipped through the same waterway. 

Now that the strait is closed, “alternatives require additional cost, additional delay, and don’t sit with the integrated supply chain that already exists,” said Marco Forgione, director general with the Institute of Export and International Trade.

Diverting ships around Africa adds up to two weeks to journey times, creating additional cost and congestion at ports.

3. What is the West doing about it?

Over the weekend, the American destroyer USS Carney and U.K. destroyer HMS Diamond shot down over a dozen drones. Earlier this month, the French FREMM multi-mission frigate Languedoc also intercepted three drones, including with Aster 15 surface-to-air missiles. 

Now, Washington is seeking to lead an international operation to ramp up efforts against the Iran-backed group, under the umbrella of the Combined Maritime Forces and its Task Force 153. 

“It’s a reinsurance operation for commercial ships,” said Héloïse Fayet, a researcher at the French Institute for International Relations (IFRI), adding it’s still unclear whether the operation is about escorting commercial vessels or pooling air defense capabilities to fight against drones and ballistic missiles. 

4. Who is taking part?

On Tuesday, the U.K. announced HMS Diamond would be deployed as part of the U.S.-led operation.

After a video meeting between Austin and Italian Defense Minister Guido Crosetto, Italy also agreed to join and said it would deploy the Virginio Fasan frigate, a 144-meter military vessel equipped with Aster 30 and 15 long-range missiles. The ship was scheduled to begin patrolling the Red Sea as part of the European anti-piracy Atalanta operation by February but is now expected to transit the Suez Canal on December 24.

France didn’t explicitly say whether Paris was in or out, but French Armed Forces Minister Sébastien Lecornu told lawmakers on Tuesday that the U.S. initiative is “interesting” because it allows intelligence sharing.

“France already has a strong presence in the region,” he added, referring to the EU’s Atalanta and Agénor operations.  

However, Spain — despite being listed as a participant by Washington — said it will only take part if NATO or the EU decide to do so, and not “unilaterally,” according to El País, citing the government.

5. Who isn’t?

Lecornu insisted regional powers such as Saudi Arabia should be included in the coalition and said he would address the issue with his Saudi counterpart, Prince Khalid bin Salman Al Saud, in a meeting in Paris on Tuesday evening. 

According to Bradley Bowman, senior director of the Center on Military and Political Power at Washington’s Foundation for Defense of Democracies, a number of Middle Eastern allies appear reluctant to take part.

“Where’s Egypt? Where is Saudi Arabia? Where is the United Arab Emirates?” he asked, warning that via its Houthi allies Iran is seeking to divide the West and its regional allies and worsen tensions around the Israel-Hamas war.

China also has a base in Djibouti where it has warships, although it isn’t in the coalition.

6. What do the Red Sea attacks mean for global trade?

While a fully-fledged economic crisis is not on the horizon yet, what’s happening in the Red Sea could lead to price increases.

“The situation is concerning in every aspect — particularly in terms of energy, oil and gas,” said Fotios Katsoulas, lead tanker analyst at S&P Global Market Intelligence.

“Demand for [maritime] fuel is already expected to increase up to 5 percent,” he said, and “higher fuel prices, higher costs for shipping, higher insurance premiums” ultimately mean higher costs for consumers. “There are even vessels already in the Red Sea that are considering passing back through the Suez Canal to the Mediterranean, even if they’d have to pay half a million dollars to do so.”

John Stawpert, a senior manager at the International Chamber of Shipping, said that while “there will be an impact in terms of the price of commodities at your supermarket checkout” and there may be an impact on oil prices, “there is still shipping that is transiting the Red Sea.” 

This is not “a total disruption” comparable to the days-long blockage of the canal in 2021 by the Ever Given container ship, he argued. 

Forgione, however, said he was “concerned that we may end up with a de facto blockade of the Suez Canal, because the Houthi rebels have a very clear agenda.”

7. Why are drones so hard to fight?

The way the Houthis operate raises challenges for Western naval forces, as they’re fending off cheap drones with ultra-expensive equipment. 

Aster 15 surface-to-air missiles — the ones fired by the French Languedoc frigate — are estimated to cost more than €1 million each while Iran-made Shahed-type drones, likely used by the Houthis, cost barely $20,000. 

“When you kill a Shahed with an Aster, it’s really the Shahed that has killed the Aster,” France’s chief of defense staff, General Thierry Burkhard, said at a conference in Paris earlier this month. 

However, if the Shahed hits a commercial vessel or a warship, the cost would be a lot higher.

“The advantage of forming a coalition is that we can share the threats that could befall boats,” IFRI’s Fayet said. “There’s an awareness now that [the Houthis] are a real threat, and that they’re able to maintain the effort over time.”  

With reporting by Laura Kayali, Antonia Zimmermann, Gabriel Gavin, Tommaso Lecca, Joshua Posaner and Geoffrey Smith.