The Kerreri ridge, to which reference has so frequently been made, consists of two main features, which rise to the height of about 300 feet above the plain, are each above a mile long, and run nearly east and west, with a dip or trough about 1,000 yards wide between them. The eastern ends of these main ridges are perhaps 1,000 yards from the river, and in this intervening space there are several rocky under-features and knolls. The Kerreri Hills, the spaces between them, and the smaller features are covered with rough boulders and angular stones of volcanic origin, which render the movements of horses and camels difficult and painful. The cavalry horses and camels were in the dip between the two ridges; and the dismounted men of the Camel Corps were deployed along the crest of the most southerly of the ridges, with their right at the desert end. Next in order to the Camel Corps, the centre of the ridge was occupied by the dismounted cavalry. The Horse Artillery were on the left. The remainder of the cavalry waited in the hollow behind the guns. The tempestuous advance of Osman soon brought him into contact with the mounted force. His real intentions are still a matter of conjecture. Whether he had been ordered to attack the Egyptian brigade, or to drive back the cavalry, or to disappear behind the Kerreri Hills in conformity with Ali-Wad-Helu, is impossible to pronounce. His action was, however, clear. He could not safely assail the Egyptians with a powerful cavalry force threatening his left rear. He therefore continued his move across the front of the zeriba. Keeping out of the range of infantry fire, bringing up his right, and marching along due north, he fell upon Broadwood. This officer, who had expected to have to deal with small bodies on the Dervish flank, found himself suddenly exposed to the attack of nearly 15,000 men, many of whom were riflemen. The Sirdar, seeing the situation from the zeriba, sent him an order to withdraw within the lines of infantry. Colonel Broadwood, however, preferred to retire through the Kerreri Hills to the northward, drawing Osman after him. He replied to that effect.