A mysterious airstrip being built on a remote island in Yemen is nearing completion, satellite photos show, one of several built in a nation mired in a stalemated war threatening to reignite.

The airstrip on Abd al-Kuri Island, which rises out of the Indian Ocean near the mouth of the Gulf of Aden, could provide a key landing zone for military operations patrolling that waterway. That could be useful as commercial shipping through the Gulf and Red Sea — a key route for cargo and energy shipments heading to Europe — has halved under attacks by Yemen’s Iranian-backed Houthi rebels. The area also has seen weapons smuggling from Iran to the rebels.

While the Houthis have linked their campaign to the Israel-Hamas war in the Gaza Strip, experts worry a ceasefire in that conflict may not be enough to see the rebels halt a campaign that’s drawn them global attention. Meanwhile, the Houthis have lobbed repeated attacks at Israel, as well as U.S. warships operating in the Red Sea, raising fears that one may make it through and endanger the lives of American service members.

A battlefield miscalculation by Yemen’s many adversarial parties, new fatal attacks on Israel or a deadly assault on an American warship easily could shatter the country’s relative calm. And it remains unclear just how President-elect Donald Trump, who will be inaugurated on Monday, will handle the emboldened rebel group.

“The Houthis feed off war — war is good for them,” said Wolf-Christian Paes, a senior fellow at the International Institute for Strategic Studies who studies Yemen. “Finally they can live up to their slogan, which famously, of course, declares, ‘Death to America, death to the Jews.’ They see themselves as being in this epic battle against their archenemies and from their view, they’re winning.”