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John III Doukas Vatatzes was the Autocrat of the Romans, the head of the Byzantine Empire, from 1221 to 1254. He was a member of the Doukas family, and was the son of Theodore I Laskaris. John III was a skilled military leader, and he successfully defended the empire from the incursions of the Seljuk Turks. He also expanded the empire by conquering new territory in Asia Minor.