What is strategic about the location of the city of Khartoum?

Explanation:

Khartoum, Arabic Al-Khartoum city, executive capital of Sudan, just south of the confluence of the Blue and White Nile rivers. It has bridge connections with its sister towns, Khartoum North and Omdurman, with which it forms Sudan’s largest conurbation. Originally an Egyptian army camp (pitched 1821), Khartoum grew into a garrisoned army town. The Mahdists besieged and destroyed it in 1885 and killed Major General Charles George Gordon, then the British governor-general of the Sudan. Reoccupied in 1898, Khartoum was rebuilt by Governor-General Lord Kitchener and served as the seat of the Anglo-Egyptian Sudan government until 1956, when the city became the capital of the independent republic of Sudan.

The Republican Palace in Khartoum city, The Sudan