Kaykhusraw, having failed to persuade Theodore to abdicate in favor of Alexios, marches against Theodore a second time with Seljuq forces in the spring of 1211.
The Seljuq army, meeting in battle in the Meander Valley near Antioch-on-the-Meander, is initially victorious, with Laskaris' eight hundred Latin mercenary cavalry bearing the brunt of the casualties due to their impetuous charge; once exhausted by their onset, the Latins are struck in the flank and rear by the Seljuq forces.
However, the Seljuq troops stop to plunder the Nicaean camp, allowing Theodore's forces to rally and counterattack the now disorganized Turks.
Theodore seeks out Kaykhusraw I and engages him in single combat, killing him.
Sources relate that Laskaris was initially unhorsed by the sultan, but he subsequently brought Kaykhusraw down by hacking at his mount's legs; once the sultan was thrown to the ground Laskaris stabbed him to the heart.
The Seljuq forces are routed.
The former emperor Alexios, Laskaris' father-in-law, is captured during the battle and subsequently imprisoned, ending his days in enforced monastic seclusion at Nicaea.
Known also as the Battle of Alaşehir, the Turkish defeat ensures continued Nicaean hegemony of the Aegean coast of Asia Minor.
The battle has freed Nicaea from Seljuq pressure but Laskaris' army has suffered heavily.
In particular his very effective Latin mercenary cavalry has been almost destroyed.
As a result, Laskaris cannot adequately defend his territory from an attack by the Latin Empire of Constantinople and he has to cede some territory bordering the Sea of Marmara.
However, the victory gives Laskaris considerable prestige and the capture of Alexios ended internal opposition to his rule.
The battle is the last major encounter between the Seljuqs and the Greeks.
Ultimately, the Seljuqs have failed to take all of Asia Minor.
