Yet after many years the hour of vengeance was at hand. The British Government had taken the pacification of the Sudan in hand, and in 1898 an army composed of British and Egyptian troops was advancing quietly and surely up the Nile. There was no need to hurry, and every step was made with prudence and consideration. The leader, General Kitchener, the last man to send a letter to Gordon, made his plans with such foresight and skill that he could calculate two years in advance almost the very day when Khartum and Omdurman would be in his hands. At the Atbara, the great tributary of the Nile which flows down from the mountains of Abyssinia, Kitchener inflicted his first great defeat on the Khalifa's army in a bloody battle. From Atbara the troops pushed on to Metemma without further fighting, and on August 28 they were only four days' march from Khartum. The green of acacia and mimosa is now conspicuous on the banks of the river, which is very high. The grey gunboats pass slowly up the Nile in the blazing sun, and the troops push on as steadily and as surely as they have from the start of the expedition. Small parties of mounted dervishes are seen in the far distance. The country becomes more diversified, and the route runs through clumps of bushes and between hillocks. A short distance in front are seen white tents, flags, and horsemen, and the roll of drums is heard. It is the Khalifa calling his men to the fight; but at the last moment the position is abandoned, the dervishes retire, and Kitchener's army continues its march. At length the vaulted dome over the Mahdi's grave beside the Nile bank rises above the southern horizon, and round about it are perceived the mud houses and walls of Omdurman. Between the town and the attacking army stretches a level sandy plain scantily clothed with yellow grass; and here took place a battle which will not be forgotten for centuries throughout the Sudan.