From late April 1916, after a German-led Ottoman force attacked British yeomanry at Katia, British Empire forces in the region at first doubled from one brigade to two and then grew as rapidly as the developing infrastructure could support them. The construction of the railway and a water pipeline soon enabled an infantry division to join the light horse and mounted rifle brigades at Romani. During the heat of summer, regular mounted patrols and reconnaissance were carried out from their base at Romani, while the infantry constructed an extensive series of defensive redoubts. On 19 July the advance of a large German, Austrian and Ottoman force across the northern Sinai was reported. From 20 July until the battle began, the Australian 1st and 2nd Light Horse Brigades took turns pushing out to battle the advancing hostile column.