I thank that it is the Indian Removal Act.
I don't know but what I always do is just Google it and the answer literally pops up.
Placing a Discharge Calendar
hope this helped! (:
The eastern and western deserts prevented invaders from the east and west. The deserts were a hard climate to travel through. Therefore, nobody could walk across to conquer Egypt. Furthermore, the cataracts in the Nile to the south protected the Egyptians from lands below them. So the answer would be that The Nile protected the Egyptians from invasion.
