Walker now oversaw the 1st Division's preparations for the August Offensive in which the division would play a supporting role to the main attack by the New Zealand and Australian Division and the British IX Corps landing at Suvla. The 1st Division's main task was a diversionary attack at Lone Pine. A secondary action was an attack on German Officers' Trench from which Turkish machine guns enfiladed neighbouring positions, notably Quinn's Post and the Nek. Lone Pine became the only time during the campaign in which Anzac forces captured and held a Turkish trench system. The attack on German Officers' Trench was to be made at midnight, 7 August, by the Australian 6th Battalion (2nd Brigade), commanded by Lieutenant-Colonel H. G. Bennett. When the first attempt failed, Walker assumed that the attack had been mishandled and so ordered another attempt to be made. When this second attempt also failed, Walker, aware that failure here would jeopardise later attacks at other points, ordered a third attempt but upon receiving further negative reports, he approached Birdwood and got approval to call off the assault. It is from this episode that Walker learnt never to repeat an attack without modifying the plan to address the causes of its failure. On 29 September Walker was buried when a shell exploded in his dugout and two weeks later, on 13 October, he was severely wounded by a machine gun while visiting the front-line.