Towards the end of November the Khalifa had begun to realise that the Turks did not mean to advance any further till the next flood of the river. He perceived that the troops remained near Berber, and that the railway was only a little way south of Abu Hamed. The blow still impended, but it was delayed. As soon as he had come to this conclusion, he no longer turned a deaf ear to Mahmud's solicitations. He knew that the falling Nile would restrict the movements of the gunboats. He knew that there were only 2,000 men in Berber--a mere handful. He did not realise the tremendous power of rapid concentration which the railway had given his enemies; and he began to think of offensive operations. But Mahmud should not go alone. The whole strength of the Dervish army should be exerted to drive back the invaders. All the troops in Omdurman were ordered north. A great camp was again formed near Kerreri. Thousands of camels were collected, and once more every preparation was made for a general advance. At the beginning of December he sent his own secretary to Mahmud to explain the plan, and to assure him of early reinforcements and supplies. Lastly, Abdullah preached a new Jehad, and it is remarkable that, while all former exhortations had been directed against 'the infidel'--i.e., those who did not believe in the Mahdi--his letters and sermons on this occasion summoned the tribes to destroy not the Egyptians but the Christians. The Khalifa had no doubts as to who inspired the movement which threatened him. There were at this time scarcely 150 Europeans in the Soudan; but they had made their presence felt. The Sirdar was returning from Kassala when the rumours of an intended Dervish advance began to grow. Every scrap of information was assiduously collected by the Intelligence Department, but it was not until the 18th of December, just as he reached Wady Halfa, that the General received apparently certain news that the Khalifa, Mahmud, all the Emirs, and the whole army were about to march north. There can be no doubt that even this tardy movement of the enemy seriously threatened the success of the operations. If the Dervishes moved swiftly, it looked as if a very critical engagement would have to be fought to avoid a damaging retreat. Sir H. Kitchener's reply to the Khalifa's open intent was to order a general concentration of the available Egyptian army towards Berber, to telegraph to Lord Cromer asking for a British brigade, and to close the Suakin-Berber route.