From Real Crusades History:

Crac de Chevaliers is located in what is now Syria near the Lebanese border. It sits at an elevation of 650 meters or 2,100 feet, atop a hill in the so-called “Homs Gap.” The latter is the most accessible route between the crusader city of Tripoli and the then important Muslim city of Homs, just 54 miles away. It dominates a fertile valley with abundant rainfall (for the region), which gave it double importance as a bulwark against invasion and a defensive structure to protect the local farmers.

The first fortification on this site was constructed in 1131 by the Kurdish Emir of Homs  as a defense against the Shiite Fatamids. It was known as Hosn al-Akrad, the Castle of the Kurds. During the first crusade, Raymond of Toulouse’s foragers came under attack from the garrison of fortress. The next day Raymond’s main force drove the attacks off and briefly occupied the castle itself before continuing south toward Jerusalem.

The crusaders did not attempt to establish their own fortification here until 1110, when Tancred, Prince of Galilee, took control of the site. Although we know a castle of some sort was constructed at this time, nothing remains of it. The castle passed at from Tancred to the Count of Tripoli at an unrecorded date.

In 1144, the Count of Tripoli, recognizing his vulnerability to Saracen attack and the limits of his own purse, made the strategic decision to what we would now call “out-source” a large part of the defense of his county to the Knights Hospitallers. He transferred to them four castles on the borders of his county, Felicium, Castellum Bochee, Lacum, and Crac de Cheveliers. The Hospitallers were in a far better position to construct, maintain and man these castles because they could draw on immense resources donated to them from across Christendom as opposed to being dependent on the revenues of a single, vulnerable county in the Holy Land.

Read the whole thing. Tom MacMaster adds: “Its twentieth and twenty first century history is also worth discussing (much of what was visible to tourists was not original but reconstruction work done by the French during their occupation (1920-1946) and it was the location of a town before that).”