The British mounted troops had been marching and fighting continuously since October 31, 1917, and had advanced a distance of seventy-five miles, measured in a straight line from Asluj to Jaffa. Other troops, after heavy fighting at Gaza, had advanced in nine days a distance of about forty miles, with two severe engagements and continual advance-guard fighting. The 52d Division had covered sixty-nine miles in this period. The railway was being pushed forward as rapidly as possible, and every opportunity was taken of landing stores at points along the coast. The landing of stores was dependent on a continuance of favorable weather, and might at any moment be stopped for several days together. A pause was therefore necessary to await the progress of railway construction, but before the British position in the plain could be considered secure it was essential to obtain a hold of the one good road which traverses the Judean range from north to south, from Nablus to Jerusalem. The west side of the Judean range consists of a series of spurs running east and west, and separated from one another by narrow valleys. These spurs are steep, bare, and stony for the most part, and in places precipitous. Between the foot of the spur of the main range and the coastal plain is the low range known as the Shephelah. On the line intended for the British advance only one good road, the main Jaffa-Jerusalem road, traversed the hills from east to west. For nearly four miles, between Bab el Wad (two-and one-half miles east of Latron) and Saris, this road passes through a narrow defile, and it had been damaged by the Turks in several places. The other roads were mere tracks on the side of the hill or up the stony beds of wadis, and were impracticable for wheeled transport without improvement. Throughout these hills the water supply was scanty without development. On November 17, 1917, the Yeomanry had commenced to move from Ramleh through the hills direct on Bireh by Annabeh, Berfilya, and Beit ur el Tahta (Lower Beth Horon). By the evening of November 18, 1917, one portion of the Yeomanry had reached the last-named place, while another portion had occupied Shilta. The route had been found impossible for wheels beyond Annabeh. On November 19, 1917, the British infantry commenced its advance. One portion was to advance up the main road as far as Kuryet el Enab, with its right flank protected by Australian mounted troops. From that place, in order to avoid any fighting in the close vicinity of the Holy City, it was to strike north toward Bireh by a track leading through Biddu. The remainder of the infantry was to advance through Berfilya to Beir Likia and Beit Dukka, and thence support the movement of the other portion. After capturing Latron and Amnas on the morning of November 19, 1917, the remainder of the day was spent in clearing the defile up to Saris, which was defended by hostile rear guards.