Theodore II Laskaris (1221/1222–1258) was a Byzantine emperor who ruled the Empire of Nicaea from 1254 until his death. Nicaea was a successor state to the Byzantine Empire, after crusaders captured the Byzantine capital, Constantinople, in 1204 during the Fourth Crusade. Theodore began to write treatises on theological, historical and philosophical themes in his youth. From around 1242, he was co-ruler with his father, and his relationship with some prominent aristocrats grew tense. Succeeding his father in 1254 Theodore replaced many aristocratic officials and generals with loyalists, including some of low birth. In 1256, he repelled a Bulgarian invasion of Thrace and Macedonia and forced Epirus to cede Dyrrachium on the Adriatic Sea. Epirus allied with Serbia and Sicily, and jointly invaded Nicaea in 1257; Nicaea's new generals could not resist the invasion. Theodore died in 1258, leaving an underage son, John IV. Michael Palaiologos seized the regency, and usurped the throne soon after. (Full article...)