Battle of Nicaea

From May 14 to June 19, 1097, the armies of the First Crusade surrounded Nicaea, capital of Kilij Arslan. The French contingents, led by Godfrey of Bouillon, Raymond of Saint-Gilles and Bohémond, established countervallation lines while the Byzantine fleet of Manuel Boutoumites locked Lake Askania. The repeated assaults on the walls, combined with the failed return of Kilij Arslan, led to the negotiated capitulation of the garrison for the benefit of the Byzantine Empire.

Nicaea controls access to western Anatolia. Western chroniclers underline the latent rivalry between crusader leaders and Byzantine officers, because Alexios I Comnenus wanted to recover the city intact. Kilij Arslan, on campaign against the Danichmends, underestimated the Frankish threat and only returned after the siege had been completely installed. The Crusaders built wooden towers, battering rams and throwing machines, while repelling several Seljuk sorties.

The crusaders alternate attacks concentrated on the gates of Leontos and Saint-Georges with undermining operations aimed at weakening the towers. The Byzantines transported siege engines by boat and blocked the city's lake supplies. Kilij Arslan launched a breakthrough attempt on June 16, repulsed by a line of stakes and Frankish heavy cavalry; isolated and deprived of water, the garrison preferred to negotiate its surrender with the imperials.

The surrender orchestrated by Boutoumites, who raised the imperial standard before those of the crusaders, caused an initial friction between allies but ensured the restitution of Nicaea to Byzantium. The crusaders received provisions, pay and guides there, then set off again towards the Anatolian interior. Kilij Arslan, humiliated, reorganizes his forces to prepare the ambush of Dorylaeus.