Theodore's early life is obscure. After the Fourth Crusade captured Constantinople in 1204, he followed Theodore Laskaris to Asia Minor, where Laskaris founded the Empire of Nicaea. Theodore's service under Laskaris is relatively unknown except for a brief reference in a letter written by the Metropolitan of Corfu, George Bardanes, one of Theodore's apologists. Bardanes writes that Theodore "took many dangers for his sake and wrested many fortresses from the enemies and subdued them to Laskaris' rule", distinguishing himself through his valour and receiving many rewards from the Nicaean ruler. Some modern scholars, such as Karl Hopf and Antoine Bon, have identified a certain Theodore, who appears as "lord of Argos" and was the successor of Leo Sgouros in leading the resistance against the Crusaders in the northwestern Peloponnese after Sgouros' death in 1208, with Theodore Komnenos Doukas. This view has been questioned by Raymond-Joseph Loenertz, who argues that there is no evidence for such an assumption, and that conversely it is well established that Theodore was in Nicaean service at the time.