Battle of Poimanenon

The Battle of Poimanenon or Poemanenum was fought in early 1224 (or possibly late 1223) between the forces of two of the main successor states of the Byzantine Empire, the Latin Empire and the Byzantine Greek Empire of Nicaea.

Since the Treaty of Nymphaeum in 1214, the Latin Empire had controlled the northwestern littoral of Asia Minor, from Nicomedia to Adramyttium, as well as the Mysian plain. In 1222, the energetic founder of the Nicaean Empire, Theodore I Laskaris, died, and was succeeded by his son-in-law, John III Doukas Vatatzes. The succession was disputed by Theodore's brothers, the sebastokratores Isaac and Alexios, who rose up in revolt and requested the aid of the Latin emperor, Robert of Courtenay. At the head of a Latin army, they marched against Vatatzes. The two armies met at Poimanenon, near a church dedicated to the Archangel Michael. In the ensuing battle, Vatatzes achieved a decisive victory; among the captives taken were the two Laskaris brothers, who were blinded.

This victory opened up the way for the recovery of most of the Latin possessions in Asia. Threatened both by Nicaea in Asia and Epirus in Europe, the Latin emperor sued for peace, which was concluded in 1225. According to its terms, the Latins abandoned all their Asian possessions except for the eastern shore of the Bosporus and the city of Nicomedia with the surrounding region.