 It was primarily used by the kings of León and Castile, but it also found currency in the Kingdom of Navarre and was employed by the counts of Castile and at least one duke of Galicia.It signalled at various points the king's equality with the rulers of the Byzantine Empire and Holy Roman Empire, his rule by conquest or military superiority, his rule over several ethnic or religious groups, and his claim to suzerainty over the other kings of the peninsula, both Christian and Muslim.The use of the imperial title received scant recognition outside of Spain and it had become largely forgotten by the thirteenth century.