In 1140, Masyaf was captured by the Nizari Ismailis, a sect of Ismaili Shia Muslims who had been exiled from their previous stronghold in Alamut in modern-day Iran.
The fortress was being defended by a Banu Munqidh mamluk (slave warrior) named Sunqur, who the Ismaili force managed to ambush and kill.
The Ismailis had chosen Syria as their new home and successively settled in the cities of Aleppo and Damascus and the fortress of Banias, each time being persecuted and massacred by the authorities or mobs of local residents incited by clerics who accused the Ismailis of being heretics or causing problems.
Consequently, the surviving Ismaili leadership decided that establishing bases in Syria's cities and thus relying on the goodwill of various umara (princes) was untenable.
Instead, they chose to settle in Jabal Ansariyah, a coastal mountain range dotted with fortresses, including Masyaf.

Following its capture, Masyaf served as the principal fortress for the Ismailis' chief da'i.
Together with other fortresses acquired at around the same time, including al-Kahf, Khawabi, al-Qadmus and al-Rusafa, the Ismailis were able to carve an autonomous territory for themselves amid hostile Crusader states and local Muslim dynasties nominally affiliated with the Abbasid Caliphate.
Masyaf served as the headquarters of the Ismaili da'i Rashid ad-Din Sinan and his elite unit of fida'i who were known as the Assassins.

In the mid-1170s, the Ayyubid sultan Saladin set about conquering Syria, ousting the Crusaders and uniting the Muslim world under Sunni Islam.
The Ismailis considered Saladin a more dangerous threat than the Crusaders and allied with Saladin's rival in Aleppo to defeat the Ayyubids.
Sinan's men launched two unsuccessful attempts to assassinate Saladin and in 1176, Saladin launched a punitive expedition against the Assassins in the strongly-defended fortress of Masyaf.
Within a few days of the siege, Saladin withdrew due to an urgent need to redeploy against the Crusaders who were attacking Ayyubid territory in the Beqaa.
He arranged a truce with Sinan mediated by the Ayyubid emir of Hama, Shihab al-Din Mahmud al-Harimi, Saladin's uncle.
In 1140, Masyaf was captured by the Nizari Ismailis, a sect of Ismaili Shia Muslims who had been exiled from their previous stronghold in Alamut in modern-day Iran. The fortress was being defended by a Banu Munqidh mamluk (slave warrior) named Sunqur, who the Ismaili force managed to ambush and kill. The Ismailis had chosen Syria as their new home and successively settled in the cities of Aleppo and Damascus and the fortress of Banias, each time being persecuted and massacred by the authorities or mobs of local residents incited by clerics who accused the Ismailis of being heretics or causing problems. Consequently, the surviving Ismaili leadership decided that establishing bases in Syria's cities and thus relying on the goodwill of various umara (princes) was untenable. Instead, they chose to settle in Jabal Ansariyah, a coastal mountain range dotted with fortresses, including Masyaf.
Following its capture, Masyaf served as the principal fortress for the Ismailis' chief da'i. Together with other fortresses acquired at around the same time, including al-Kahf, Khawabi, al-Qadmus and al-Rusafa, the Ismailis were able to carve an autonomous territory for themselves amid hostile Crusader states and local Muslim dynasties nominally affiliated with the Abbasid Caliphate. Masyaf served as the headquarters of the Ismaili da'i Rashid ad-Din Sinan and his elite unit of fida'i who were known as the Assassins.
In the mid-1170s, the Ayyubid sultan Saladin set about conquering Syria, ousting the Crusaders and uniting the Muslim world under Sunni Islam. The Ismailis considered Saladin a more dangerous threat than the Crusaders and allied with Saladin's rival in Aleppo to defeat the Ayyubids. Sinan's men launched two unsuccessful attempts to assassinate Saladin and in 1176, Saladin launched a punitive expedition against the Assassins in the strongly-defended fortress of Masyaf. Within a few days of the siege, Saladin withdrew due to an urgent need to redeploy against the Crusaders who were attacking Ayyubid territory in the Beqaa. He arranged a truce with Sinan mediated by the Ayyubid emir of Hama, Shihab al-Din Mahmud al-Harimi, Saladin's uncle.
Masyaf