Meanwhile in the Soudan triumphant barbarism had produced an appalling state of things. It is impossible to exaggerate the hideousness of the regime of Mahdism. A ferocious tyranny terrorised and reduced to desolation the whole of the upper basin of the Nile; and the population is said to have shrunk from 12,000,000 to 2,000,000, although exact figures are of course unattainable. One of the evil consequences of this regime was that it prevented a scientific treatment of the flow of the Nile, on which the very life of Egypt depended. Scientific irrigation had already worked wonders in increasing the productivity of Egypt, but to complete this work, and to secure avoidance of the famines which follow any deficiency in the Nile-flow, it was necessary to deal with the upper waters of the great river. On this ground, and in order to remove the danger of a return of barbarism, which was threatened by frequent Mahdist attacks, and finally in order to rescue captives who were enduring terrible sufferings in the hands of the Mahdi, it appeared that the reconquest of the Soudan must be undertaken as the inevitable sequel to the reorganisation of Egypt. It was achieved, with a wonderful efficiency which made the name of Kitchener famous, in the campaigns of 1896-98. The reconquered province was nominally placed under the joint administration of Britain and Egypt; but in fact the very remarkable work of civilisation which was carried out in it during the years preceding the Great War was wholly directed by British agents and officers.