The largest ancient fortress ever found in Egypt has been unearthed near the Suez Canal, and it seems to date to around 1000 B.C., or sometime during the waning years of the New Kingdom:
The fort was part of the Horus Military Route, which protected Egypt’s eastern front. Five of the 11 forts that made up the route, described on the walls of the Karnak Temple in Luxor, have been found.
The article does not state it, but could this have been built in response to the Battle of Qadesh (1274 B.C.) with the Hittites which was basically left unresolved? Or were there other foes in the area (e.g. Assyrians) who posed a greater threat to the Egyptians at this time?