The 31st Battalion was raised as part of the 8th Brigade at Enoggera, on the outskirts of Brisbane, in August 1915. Some of the battalion's companies, however, were also raised at Broadmeadows Camp in Victoria. In early October, these two elements were united at Broadmeadows, and the battalion sailed from Melbourne the following month.

The 8th Brigade joined the newly raised 5th Australian Division in Egypt, and proceeded to France, destined for the Western Front, in June 1916. The 31st Battalion fought its first major battle at Fromelles on 19 July 1916, having only entered the front-line trenches 3 days previously. The attack was a disastrous introduction to battle for the 31st - it suffered 572 casualties, over half of its strength. Although it still spent periods in the front line, the 31st played no major offensive role for the rest of the year.

In early 1917, the German Army withdrew to the Hindenburg Line allowing the British front to be advanced and the 31st Battalion participated in the follow-up operations. The battalion subsequently missed the heavy fighting to breach the Hindenburg Line during the second battle of Bullecourt as the 8th Brigade was deployed to protect the division's flank. The only large battle in 1917 in which the 31st Battalion played a major role was Polygon Wood, fought in the Ypres sector in Belgium on 26 September.

Unlike some AIF battalions, the 31st had a relatively quiet time during the German Spring Offensive of 1918 as the 5th Division was largely kept in reserve. The Allies launched their own offensive with the battle of Ameins on 8 August, in which the 31st Battalion participated. It was subsequently involved in the operations that continued to press the retreating Germans through August and into September. The 31st fought its last major action of the war in September 1918 when the 5th and 3rd Australian Divisions, and two American divisions attacked the Hindenburg Line across the top of the 6-kilometre-long St Quentin Canal tunnel; the canal was a major obstacle in the German defensive scheme. The 31st was resting and retraining out of the line when the war ended on 11 November 1918. It disbanded in France on 21 March 1919.

Reference
  • AWM4/23/48/1-23/48/44: 31st Battalion war diary
Conflict First World War, 1914-1918
Related events
Battle honours
Commanding officers
Decorations
  • 1 VC; 1 DSO and 1 bar; 2 OBE; 20 MC and 2 bars; 1 AlbM; 11 DCM; 68 MM, 8 bars and 1 2nd bar; 4 MSM; 6 foreign awards
Alternative names
  • 31 Battalion
  • 31 Battalion (Infantry)
  • 31 Bn
  • 31 Infantry Battalion
  • 31st Battalion
  • 31st Battalion (Infantry)
  • 31st Battalion Attached 52nd Divisional Headquarters
  • 31st Battalion Attached 5th Australian Division
  • 31st Battalion Attached 8th Light Trench Mortar Battery
  • 31st Battalion Attached Headquarters 5th Australian Division
  • 31st Battalion Attached Light Trench Mortar Battery
  • 31st Battalion Attached No 2 Section 5th Division Signal Company, Engineers
  • 31st Bn
  • 31st Bn (5th DS Co)
  • 32nd Battalion Attached 5th Division Signal Company Engineers
  • Australian Army Medical Corps Attached 31st Battalion
  • Headquarters 31st Battalion