Forced conversions under Leon III, Basil I, Romanus I Lecapenus

Three emperors of Constantinople attempted, three centuries apart, to obtain by compulsion what preaching could not achieve: the disappearance of Judaism from the Byzantine Empire.

Leon III ordered the baptism of Jews and Montanists; chroniclers report that many outwardly complied while continuing to live according to the Law, which made the measure a failure on its own terms. Basil I resumed the method with some moderation: public disputations, tax exemptions and promised offices for converts, compulsion for the rest. Under Romanos Lekapenos, the campaign was the harshest, and it drove entire communities to seek refuge beyond the borders — toward Khazaria, whose rulers were reputed to have embraced Judaism.

None of these three waves outlasted its author: successors allowed the baptized to return, and the Jewish presence in Constantinople, Thebes, or Salonique was never interrupted.