Say the 25th or 26th Dynasty of Ancient Egypt wary of the threat coming from the east (Neo-assyrian & , neo-babylonian respectively) decide they'll build a great wall (a la the Great wall of China) from the Atlantic to the Arabian sea w/ a series of fortifications ahead of them in the Sinai peninsula.
How do they fair against the Persian Empire w/ these defences in place?
(I recognise they'll be issues, the terrain appears to be rather flat, but humour me)
Edit: Red not Arabian sea. Mediterranean not Atlantic