On 1 September, the 6th Brigade (21st, 22nd, 23rd and 24 Battalions) seized the summit on their second attempt. The 14th Brigade of the 5th Division (53rd, 54th, 55th and 56th Battalions) captured the woods north of Peronne and after pressing on during a short-lived German attack, took the main part of Peronne. An attempt to pass the northern side of the town was stopped by heavy fire from the ramparts. On 2 September the 7th Brigade (25th, 26th, 27th and 28th battalions) drove beyond the mount, the 15th Brigade (57th, 58th, 59th and 60th Battalions) seized the remainder of Peronne and the 3rd Division advanced on the northern flank. By the evening of the 3 September, the Australian held Peronne, captured Flamicourt the next day and then advanced two miles to the east.
Meanwhile the 3rd Army and the Canadians thrust towards Cambrai during the same period, and this gave General Ludendorff additional cause to retire from the Somme below Peronne. His only option was to retreat to the Hindenburg Line, which had been already been breached by the British near Bullecourt. The British had built three lines facing the Hindenburg line which had been captured by the Germans in the March offensive. By 11 September, the Australians had won the first of these lines by peaceful penetration, but the second and third lines were too strong and on 18 September an attack launched by the British 4th Army who despite heavy rain and fog, achieved success.
In the second stage of the advance, the Australian 1st Division on the left achieved the second and third objectives. On the right the Australian 4th Division infantry, worked its way up open valleys to the dense wired protecting the Hindenburg "Outpost" Line. By dawn on September 19, a great part of the Australian line looked down on the St Quentin Canal and the Hindenburg Line beyond. The two Australian divisions captured 4,300 prisoners and 76 guns in this offensive and it was reported that captured German soldiers had said that their men would not now face the Australians. This latter battle highlighted the low morale of the German forces and paved the way for the attack on the Hindenburg line itself.
The Battle of Mont St Quentin resulted in a strategic, tactical and psychological victory for the Australian Forces and dealt a stunning blow to five German divisions, including the elite 2nd German Guard Division, drove the enemy from one of the key positions in France, and took 2,600 prisoners at a cost of slightly over 3,000 casualties. It was fought without tanks and creeping barrages and demonstrated that rapid and flexible manoeuvring could play a decisive part in capturing enemy positions on the Western Front. Australians attacked more than their number of Germans in strong positions and captured more of them than they could safely hold.