Hülegü (Hulagu) began his westward march with a large, multi-ulus force tasked by the Great Khan Möngke with subduing key powers in southwest Asia, a campaign that would culminate in the destruction of the Nizari strongholds and the Abbasid capital.
After a prolonged advance and logistical buildup, Hülegü’s army crossed the Oxus (Amu Darya), marking the start of sustained operations in Iran and adjacent regions.
Hülegü opened the decisive phase of the anti-Nizari campaign by encircling Maymun-Diz, a principal Nizari Ismaili stronghold and seat of Imam Rukn al-Din Khurshah, using siege engines and sustained bombardment.
Khurshah surrendered and entered negotiations under Mongol pressure, a turning point that accelerated the capitulation of other Nizari fortresses and enabled Hülegü to dismantle the Alamut-state.
Mongol forces took Alamut, the symbolic heart of the Nizari Ismaili fortress network, and began dismantling it—effectively ending organized Nizari territorial rule in the Alamut region.
With the Nizari strongholds subdued, Hülegü shifted the main effort toward the Abbasid Caliphate, marching on Baghdad and demanding submission from Caliph al-Mustaʿṣim.
In the opening actions around Baghdad, a Mongol contingent sent across the Tigris suffered a setback against Abbasid forces under Aybak, prompting further Mongol countermeasures.
Mongol forces under Baiju used flooding and coordinated attacks to disrupt and drive back Abbasid troops, tightening the operational encirclement before the formal siege lines were completed.
Hülegü’s army began the siege of Baghdad, establishing siegeworks and deploying engines under commanders including the Chinese general Guo Kan to breach the city’s defenses.
Mongol siege equipment breached key defensive points, hastening the collapse of resistance and setting the stage for the city’s surrender days later.
Mongol troops seized major stretches of Baghdad’s walls, making further organized defense untenable and forcing Abbasid leaders into last-ditch negotiations.
Caliph al-Mustaʿṣim surrendered (with senior officials and notables) after the short siege, ending effective Abbasid military resistance in the city.
Mongol forces entered Baghdad and began large-scale plunder, destruction, and massacres, a watershed event that shattered the Abbasid capital’s political and cultural institutions.
Al-Mustaʿṣim was executed shortly after the city’s fall, bringing the Abbasid Caliphate in Baghdad to an end and symbolizing the transfer of regional power to Hülegü’s new order.
Hulagu's Campaigns and the Sack of Baghdad (1253–1258)
