By Nabih Bulos and Patrick J. McDonnell, Los Angeles Times

BEIRUT — The Syrian military on Thursday captured a historic Crusader castle that had long been a highly symbolic rebel bastion, the latest victory in an ongoing offensive along the Lebanese border, according to government and opposition accounts.

Krak des Chevaliers, a colossal hilltop fortress dating to the 12th century named after a medieval Crusader order, was overrun after a series of fierce battles in the nearby town of Hossen that concluded with government troops hoisting a Syrian flag above the celebrated citadel.

The image of the national colors rising above the renowned monument, a moment captured on video broadcast on Syrian state television, was a dramatic indication of how pro-government forces have gained ground in recent months against deeply divided rebels fighting to oust President Bashar Assad.

“The Syrian Arab Army raises the flag of the nation over the Krak des Chevaliers castle in Homs province after crushing the terrorists who were holed up there,” triumphant state television declared, echoing the official description of rebels as “terrorists.”

As the Syrian civil war this month entered its fourth year, the government boasted of several important advances. On Sunday, the military overran the longtime rebel stronghold of Yabroud, not far from the Lebanese border about 70 miles southeast of Krak des Chevaliers.

Sealing rebel supply and logistics lines from neighboring Lebanon has long been a major focus of the Syrian military. The capture of the castle and nearby towns, along with earlier military advances in the border zone, have curbed the rebels’ ability to ferry in supplies and fresh fighters from Lebanon.

Krak des Chevaliers, visible from the main highway from Homs city to the Mediterranean coast, had long been a high-profile symbol of opposition strength in strategic western Homs province, the gateway to central and northern Syria from Damascus, the capital.

Islamist rebels recognized the strategic benefits of the mountain-top castle just as Christian Crusaders had done centuries earlier.

The castle’s construction is attributed to the Knights Hospitaller, who held the site until it was captured in 1271 by Muslim forces.

The fortress was a major tourist attraction until the Syrian conflict broke out in March 2011. Antigovernment insurgents captured the site and surrounding towns.

The fort, a UNESCO World Heritage site, has reportedly suffered extensive damage from mortar attacks, airstrikes and gun battles. The extent of the destruction at the castle is unclear.

One little-noticed effect of the Syrian conflict has been the damage to numerous historic sites in a nation that has been a crossroads for various civilizations. The Old City of Aleppo, another World Heritage site that was a terminus of the Silk Road, also has been pummeled during the Syrian conflict, with many of its buildings and parts of its acclaimed covered market destroyed. The ruins of Palmyra, a trading hub of the Roman empire in what is now eastern Syria, has seen some of its monuments looted, authorities say.

Conservationists say it is impossible to determine the extent of the devastation to Syria’s historic patrimony until some semblance of peace is restored and experts can visit hard-hit areas and make an assessment. That may take a long time. All diplomatic efforts to end the conflict have faltered.

The Syrian Observatory for Human Rights, a British-based pro-opposition group, confirmed the fall of the Krak des Chevaliers, reporting that “no less than 12 fighters were killed … in clashes with regime forces in the countryside of Hossen.” Some accounts put the rebel death toll in the dozens.

The government’s advance, accompanied by artillery bombardment, prompted many rebels to flee to neighboring Lebanon. At least 25 wounded Syrians crossed into Lebanese territory, Lebanon’s national news agency reported.

AFP Photo/Jim Lopez