were reinforced by the recently arrived Australian 2/4th Machine-Gun Battalion. Also under Bennett's command was the 44th Indian Infantry Brigade. The III Indian Corps (Lieutenant-General Sir Lewis Heath) including the 11th Indian Infantry Division under Major-General Berthold Key with reinforcements from the 8th Indian Brigade, and the 18th Infantry Division—was assigned the north-eastern sector, known as the "Northern Area". This included the naval base at Sembawang. The "Southern Area", including the main urban areas in the south-east, was commanded by Major-General Frank Simmons. His forces consisted of elements of the 1st Malaya Infantry Brigade and the Straits Settlements Volunteer Force Brigade with the Indian 12th Infantry Brigade in reserve. From 3 February, the Commonwealth forces were shelled by Japanese artillery, and air attacks on Singapore intensified over the next five days. The artillery and air bombardment strengthened, severely disrupting communications between Commonwealth units and their commanders and affecting preparations for the defence of the island. From aerial reconnaissance, scouts, infiltrators and observation from high ground across the straits (such as at Istana Bukit Serene and the Sultan of Johor's palace), Japanese commander General Tomoyuki Yamashita and his staff gained excellent knowledge of the Commonwealth positions. Yamashita and his officers stationed themselves at Istana Bukit Serene and the Johor state secretariat building—the Sultan Ibrahim Building—to plan for the invasion of Singapore. Although his military advisors judged that Istana Bukit Serene was an easy target, Yamashita was confident that the British Army would not attack the palace because it belonged to the Sultan of Johor. Yamashita's prediction was correct; despite being observed by Australian artillery, permission to engage the palace was denied by Gordon Bennett. Most of Singapore's BL 15-inch Mk I naval guns could be traversed north and were used to engage the Japanese. The guns—which included the Johore Battery, with three guns and one battery with two guns—were supplied mostly with armour-piercing shells (AP) for anti-shipping use and few high explosive (HE) shells. Percival incorrectly guessed that the Japanese would land forces on the north-east side of Singapore, ignoring advice that the north-west was a more likely direction of attack (where the Straits of Johor were the narrowest and a series of river mouths provided cover for the launching of water craft). This was encouraged by the deliberate movement of Japanese troops in this sector to deceive the British. Much of the equipment and resources of the garrison had been