The "Karabisianoi" were established sometime in the second half of the 7th century in response to the Muslim conquests. Various scholars have suggested that it evolved from the remainders of the old "quaestura exercitus" or the late Roman field army of the Illyricum, but these suggestions remain hypothetical. The date of the fleet's establishment is unclear: some scholars propose that it was established in the 650s or 660s by Emperor Constans II (), following the major naval defeat at the Battle of the Masts in 655, while others think that it was created after the Siege of Constantinople (674–678), where the Arab advance by sea seems to have been almost unopposed. The first certain reference to the "Karabisianoi" is during the siege of Thessalonica by the Slavs in , and then in a letter of Emperor Justinian II () to Pope Conon in 687.