The Nizari Ismaili garrison of Gerdkuh, located in the mountainous regions of Persia, had remained defiant against the Mongol invasions for 17 years. The Mongols, led by Hulagu Khan, had sought to eradicate the Ismailis, viewing them as a significant threat to their authority. The siege began in the early 1250s, when Mongol forces, having already conquered vast areas of Persia and the Middle East, turned their attention to this strategic fortress. The garrison demonstrated exceptional resilience and tactical ingenuity, utilizing the rugged terrain to their advantage and sustaining a lengthy defense despite facing relentless assaults.By the time the garrison surrendered, their numbers had diminished significantly due to prolonged warfare, resource depletion, and the unyielding pressure from the Mongolian forces. Negotiations for capitulation were not taken lightly, and the Ismailis had attempted to negotiate a favorable outcome, reflecting their strategic mindset even at the brink of defeat. The Mongols, recognizing the challenges of sustaining the siege any longer amidst rising winter conditions, eventually accepted the terms. The completion of the siege and the surrender of Gerdkuh not only marked the Fall of the Nizari stronghold but also led to the consolidation of Mongol rule in Persia and surrounding regions.