Hassan-i Sabbah took the mountain fortress of Alamut in 1090 without a siege, then never left it for over three decades until his death in 1124. From that single stronghold in the Elburz Mountains he built a system of targeted elimination that paralyzed the Seljuk Empire and eventually gave the English language the word assassin.

This episode follows his early studies in Cairo, the infiltration that turned Alamut's own garrison, the concept of Dar al-Hijra, and the training of the fidai as multilingual sleeper agents practicing taqiyya. We also unpack the hashish myth spread by Marco Polo, the 1122 slur that became a word, Rashid ad-Din Sinan's dagger left beside Saladin's bed at Masyaf, and why the strategy finally collapsed against Hulagu Khan's Mongols in 1256.

• Why Hassan chose to eliminate viziers and generals in public space ...