Complex sentence: The second prefect, Aelius Gallus, made an unsuccessful expedition to conquer Arabia Petraea and even Arabia Felix; however, the Red Sea coast of Egypt was not brought under Roman control until the reign of Claudius.
Split into simpler sentences: The second prefect, Aelius Gallus, made an unsuccessful expedition to conquer Arabia Petraea and even Arabia Felix. The Red Sea coast of Egypt was not brought under Roman control until the reign of Claudius.