The explosions woke Ali Al-Sunaidar and his children in the middle of the night — a familiar feeling after years of war.

He knew that the ancient mud-brick buildings in Yemen’s capital, Sana, could collapse under the pressure released by bombings, so he opened the windows in his home, letting in the winter air.

“We were terrified and anxious,” said Mr. Al-Sunaidar, a photojournalist in Sana, after dozens of American-led airstrikes hit Yemen on Friday local time, targeting the Houthi militia that controls much of the country’s north. “We’ve been living in tension, dread and horror for the last nine years.”

A day later, the United States struck again, bombing a radar facility in Yemen, U.S. officials said.

For nearly a decade, Yemen has been at war, pummeled by a Saudi-led military coalition supplied with American bombs in an effort to defeat the Houthis — a once-scrappy tribal militia backed by Iran that has evolved into a de facto government in northern Yemen. The coalition expected swift victory. Instead, hundreds of thousands of people have died from fighting, hunger and disease, and since the coalition pulled back several years ago, partly because of international pressure, the Houthis have only deepened their grip on power.