<div class="css-s99gbd StoryBodyCompanionColumn" data-testid="companionColumn-0"><div class="css-53u6y8"><p class="css-at9mc1 evys1bk0">For more than a year, Houthi rebels in Yemen attacked merchant vessels and warships in the Red Sea with <a class="css-yywogo" href="https://www.nytimes.com/article/houthi-yemen-red-sea-attacks.html" title="">missiles, drones</a> and <a class="css-yywogo" href="https://www.nytimes.com/2024/06/12/world/middleeast/yemen-houthis-red-sea-ship.html" title="">speedboats loaded with explosives</a>, disrupting global trade through one of the world’s busiest shipping lanes.</p><p class="css-at9mc1 evys1bk0">Claiming solidarity with Palestinians in Gaza, the Houthis have hit vessels as far as 100 miles off the Yemeni coast, prompting <a class="css-yywogo" href="https://www.nytimes.com/2024/06/13/world/middleeast/yemen-houthi-red-sea-ship-attack.html" title="">retaliatory airstrikes by U.S.</a> and <a class="css-yywogo" href="https://www.nytimes.com/2024/12/26/world/middleeast/israel-yemen-bombs-houthis.html" title="">Israeli warplanes</a>.</p><p class="css-at9mc1 evys1bk0">The Houthis, who are backed by Iran, <a class="css-yywogo" href="https://www.nytimes.com/2025/01/24/business/shipping-red-sea-houthis.html" title="">largely discontinued</a> their attacks when Israel and Hamas reached a cease-fire in January. But evidence examined by weapons researchers shows that the rebels may have acquired new technology that makes drones more difficult to detect and helps them fly even farther.</p><p class="css-at9mc1 evys1bk0">“It could potentially give the Houthis an element of surprise against U.S. or Israeli military forces if they were to restart any of these conflicts,” said Taimur Khan, an investigator with <a class="css-yywogo" href="https://www.conflictarm.com/" rel="noopener noreferrer" target="_blank" title="">Conflict Armament Research</a>, a British group that identifies and tracks weapons and ammunition used in wars around the world.</p></div><aside aria-label="companion column" class="css-ew4tgv"></aside></div><div data-testid="Dropzone-1"></div><div class="css-s99gbd StoryBodyCompanionColumn" data-testid="companionColumn-1"><div class="css-53u6y8"><p class="css-at9mc1 evys1bk0">Mr. Khan traveled to southwestern Yemen in November to document parts of a hydrogen fuel cell system that government forces found in a small boat offshore, alongside other weapons known to be used by Houthi fighters.</p><p class="css-at9mc1 evys1bk0">Hydrogen fuel cells produce electricity through a reaction of oxygen in the air and compressed hydrogen across a series of charged metal plates. 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