Egypt has long understood that most of the water came from the Blue Nile and Ethiopia but has never been able to seize control of Ethiopia or threaten Ethiopia as it had done with Sudan for thousands of years. Some serious attempts to invade Ethiopia were made in the 19th century but all failed. Italy also made several attempts, and finally succeeded in the 1930s. After World War II began (in 1939) Britain came to the aid of Ethiopia and forced the Italians to withdraw. Ethiopian is the only African nation (and a major one of that) that was never colonized. Moreover the Ethiopians are largely Christian and have long resisted aggression by Moslem nations.
The Ethiopia has long resisted Egyptian pressure and threats over building new dams and other water projects on the Blue Nile River. Ethiopia, Uganda, Rwanda, and Tanzania, all containing sources of the Nile, recently announced joint action to obtain a more equitable share of Nile River water. Ethiopia believes that Egypt and Sudan claim too much water and base their claims on colonial-era agreements that are no longer valid. The main treaty was created in 1929 but few of these treaties involved Ethiopia because Ethiopia was never under colonial control and never recognized foreign nation having any claims on its water. Worse for Egypt, Sudan (which has been conquered many times by Egypt, and actually ruled Egypt for over a century in ancient times) backs Ethiopia in these water matters. Most Egyptians seem to understand the military superiority of Ethiopia and the inability of Egypt to back up its threats. Nevertheless the Egyptian public feels better when their government acts aggressively about protecting the Nile water flow.