 Complete the following phrase:  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 fleets 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 