Mustafa Kemal believed that the British would use their naval power to command the land from every side at the tip of the peninsula; at Gaba Tepe, the short distance to the eastern coast meant that the Allies could easily reach the Narrows (the right-angled bend in the middle of the Dardanelles). Sanders considered Besika Bay on the Asiatic coast to be the most vulnerable to invasion, since the terrain was easier to cross and was convenient to attack the most important Ottoman batteries guarding the straits and a third of the 5th Army was assembled there. Two divisions were concentrated at Bulair at the north end of the Gallipoli peninsula, to protect supply and communication lines to the defences further down the peninsula. The 19th Division (Kemal) and the 9th Division were placed along the Aegean coast and at Cape Helles on the tip of the peninsula. Sanders kept the bulk of the Ottoman forces inland in reserve, leaving a minimum of troops guarding the coast. The 3rd Division and a cavalry brigade arrived from Istanbul in early April, bringing the front line strength of the Ottomans to which Sanders concentrated in three groups. A maximum effort to improve land and sea communications was ordered, to move reinforcements swiftly to danger points; troops moved at night to avoid Allied air reconnaissance. Sanders' strategy was opposed by Ottoman commanders, including Kemal, who believed that the defenders were too widely dispersed to defeat the invasion on the beaches. Sanders was certain that a rigid system of defence would fail and that the only hope of success lay in the mobility of the three groups, particularly the 19th Division near Boghali, in general reserve, ready to move to Bulair, Gaba Tepe or the Asiatic shore.