An attack by U.S.-backed Saudi coalition aircraft in February obliterated the gateway and damaged the walls of the ancient Yemeni fortress town of Kawkaban. (Sudarsan Raghavan/The Washington Post)

The majestic fortress nestled atop a mountain here in northwestern Yemen survived the armies of the Islamic warrior Saladin in the 12th century. Four hundred years later, it survived invasions by Egyptians and Ottoman Turks. Through generations of rulers and wars, its walls remained intact.

Until last February.

Before dawn one morning, fighter jets from a U.S.-backed, Saudi-led coalition fired four missiles at Kawkaban, killing seven residents of the town that lies inside the citadel and pulverizing its ancient gateway. Behind the shattered walls, 700-year-old houses known for their spectacular architecture are now mounds of rubble.

Across this war-torn country, factories, hospitals and power plants have been leveled, threatening Yemen’s future. In Kawkaban and elsewhere, the past lies in ruins, too.

“There were wars that happened, but nothing ever like this one,” resident Ahmed al-Ashwal said last month.

A centuries-old house in Kawkaban destroyed in the February airstrike. (Sudarsan Raghavan/The Washington Post)

Over the past 21 months, thousands of civilians have died in the fighting in Yemen, and a humanitarian crisis is escalating. But Yemenis — aware of their country’s status as one of the world’s oldest repositories of civilization, dating back centuries before Christ — voice equal outrage about cultural losses. Armed groups, including radical Islamists, have damaged or destroyed ancient mosques and churches. Museums have been looted. Airstrikes have targeted historic sites that the United Nations Educational, Scientific and Cultural Organization (UNESCO) recognizes as unique.

The attacks are widely considered an affront to Yemen’s national pride and identity, delivered by neighbors rich in oil revenue and international support but comparatively poor in cultural heritage. The bitterness threatens to complicate peace efforts, while the destruction jeopardizes future tourism revenue, vital to rebuilding the nation.

“The scars will take a long time to heal,” said Mohannad Ahmad al-Syani, who runs the government body that oversees Yemen’s antiquities and museums.

By Syani’s count, about 85 historic sites have been “directly or indirectly targeted” by one side or another since war erupted in Yemen in March 2015. Northern Houthi rebels aligned with loyalists of former president Ali Abdullah Saleh are battling forces loyal to the exiled government of President Abed Rabbo Mansour Hadi.

A coalition of Persian Gulf countries, led by Saudi Arabia and aided by intelligence, training and other support from the Pentagon, is seeking Hadi’s restoration. The Sunni Muslim countries are wary of the Shiite Houthis and their suspected backing by Iran’s Shiite theocracy. Adding more turmoil is Yemen’s potent al-Qaeda branch and an emerging Islamic State presence.

“None of the parties show any kind of respect for the historical value of these sites,” said Radhiyah Al-Mutawakkil, the director of Mwatana, an independent Yemeni human rights group that has identified 17 cultural and architectural gems that have been damaged or destroyed.

In an email, a spokesman for the Saudi-led military coalition declined to comment on the Kawkaban assault but denied that its forces’ aircraft were targeting historic sites.

The coalition “is intervening in Yemen to safeguard the future rights, security and prosperity of the Yemeni people,” Maj. Gen. Ahmed Asiri said. “We would have no interest in damaging any aspect of Yemen’s economy or cultural heritage.”

Christopher Sherwood, a Defense Department spokesman, also declined to comment, noting that “the U.S. military does not participate in targeting, target selection or target engagement” in support of the Saudi-led coalition.

For much of its existence, Kawkaban has been a stronghold of the Shiite Zaydi sect, to which the Houthis belong. The Zaydi rulers fought back numerous foreign invaders over the centuries. When civil war erupted in the 1960s, the citadel was one of the last Zaydi holdouts, eventually surrendering to the new government. That time, too, the town was bombarded, but less catastrophically, residents said.

The February attack unfolded as Mohammed al-Bahiri was preparing for dawn prayers. As his family’s mud-brick house shook and the windows shattered, he huddled in the living room with his wife and five young children.

“We could hear the planes and see flashes of light through the windows. Then the second strike came,” said Bahiri, a teacher. “It was like being in a horror movie.”

Salim al-Amsha’s 87-year-old father did not survive. Sick in bed, he was struck by shrapnel as the ceiling collapsed, his son said. He was still breathing when Amsha pulled him out, but they were trapped in the city for two hours waiting for rubble to be cleared from the gateway.

“My father died on the way to the hospital,” Amsha said, his face anguished as he gazed at the panorama of destruction. Houses had been sheared in half. One sat atop a hill, crushed as if with a giant foot. In the rubble, remnants of lives still lay: a TV set, a mangled car, a child-size dress.

A 12-year-old boy also died in the attack.

In interviews, residents said no Houthi or Saleh loyalist fighters had ever been based here. A walk around the town revealed no sign of weapons depots or military activity.

Rebels did occupy other historically significant sites targeted by coalition jets, including a centuries-old dam in the northern city of Marib and the al-Husaini mosque and a notable military museum in the southern port city of Aden, Mwatana researchers said.

Abdul Malik Alagri, a senior Houthi political official, denied that the rebels were using cultural sites as bases or to store weapons. He said Saudi Arabia was targeting historical structures “out of hatred and envy because they have no history or cultural heritage.”

Syani disputed those claims, citing Marib as an example. When he complained that rebel artillery units were being positioned near historic sites, he said, he was told that they were there to protect the country’s heritage.

“This has really troubled us,” he said. “Any armed presence can be used as an excuse for an attack. But it’s hard to convince the fighters that locating in or near historical locations is wrong.”

In the south, militants from al-Qaeda and the Islamic State have destroyed tombs, mausoleums and churches, mirroring the targeting of shrines by their comrades in Syria and Iraq. In Hadramout province, at least 13 historic religious sites dating back hundreds of years have been destroyed, Syani said.

Last year, Islamist extremists used hoes and bulldozers to destroy the ancient Bajabar tomb and a suicide car bomb to decimate centuries-old homes in the walled city of Shibam, a UNESCO heritage site known as “the world’s oldest skyscraper city” because of its mud-brick high-rise structures. In Lahij province, militants destroyed the 800-year-old tomb of a Sufi saint.

As he talked about the destruction, Syani’s voice cracked. Then he angrily questioned why the wrecking of Yemen’s culture hasn’t received the same attention as the plundering of mosques, churches and medieval sites by the Islamic State in Syria and Iraq.

“Why is the world so quiet?” he said, shaking his head.

In the capital, Sanaa, the Old City neighborhood — also a UNESCO heritage site — has been inhabited for 2,500 years. Nabil Abdul Hamid said that, like generations of his family before him, he used to wake up daily to a view of rows of multistory, gingerbread-colored buildings with arched windows and fired brick decorated with white geometric shapes.

But now there’s a large gap, like missing teeth. After a coalition airstrike last year, four buildings crumbled. There are concerns that the foundations of other old houses nearby were weakened.

“We never expected them to target the Old City,” Abdul Hamid said. “This is like taking revenge on Yemen’s civilization.”

Many in Kawkaban feel the same way. The flow of tourists had already ebbed in recent years because of worries about terrorism and kidnappings. The February airstrike further dashed any hopes of a revival.

Tourist stalls outside the gateway are shuttered, their doors rusted. Residents have moved away, many of them too poor to rebuild their homes, let alone the gate. Their plight has deepened local animosity toward the Saudi-led coalition and its allies, especially the United States.

On the way up to Kawkaban, someone has painted a large American flag in the middle of the road.

Every visitor has to drive over it.