He is first directly mentioned in the historical writings of John Skylitzes in the 990s (ca. 994 according to Nicholas Adontz), when he was appointed by Emperor Basil II, at the time embroiled in the long war with Bulgaria, as "strategos" in Philippopolis. In the year 1000, along with Nikephoros Xiphias, he led an army that rapidly captured the Bulgarian fortresses of Great Preslav, Little Preslav (Presthlavitza) and Pliska, completing the re-imposition of Byzantine control over the northeastern portions of the Bulgarian state, first conquered by Emperor John Tzimiskes in the early 970s. Shortly after, Theodorokanos retired due to his advanced age, and was replaced by Xiphias.