The Egyptians were protected from invaders due to their geographical features. For example, they had the Mediterranean Sea to the north along with the Nile Delta. This body of water blocks off land on the other side. If intruders were to come to Egypt, they would have to go by boat.
Not everyone knows this but the large creations such as the sphinx and the pyramids scared invaders. The river Nile was also set in the perfect place where it was quite safe. They were also surrounded by desert which helped. Also a large military and walls/forts.
