The 34h Battalion became a part of the 9th Brigade of the 3rd Australian Division. On the 1st of May the Battalion left by train from Farley Station for the Showground in Sydney. Equipped with kit bags and necessary clothing, and was reviewed in Moore Park by General Ramoccotti. On the following morning of the 2nd of May 1916 the men embarked on the transport HMAT A20 "Hororata" and sailed at 4:00pm. Arriving in England in early July, the Battalion spent the next five months in training. It crossed into France on the 22nd November, and moved into the trenches of the Western Front for the first time on the 27th of November, just in time for the onset of the terrible winter of 1916-17.

The 34th Battalion had to wait until the emphasis of British and Dominion operations switched to the Ypres Section of Belgium in mid-1917 to take part in its first major battle; this was the battle of Messines, launched on the 7th June. After several stints in the trenches, and a period of rest and training, the 34th Battalion entered battle again on the 12th October around Passchendaele. The battlefield, though, had been deluged with rain, and thick mud tugged at the advancing troops and fouled their weapons. The battle ended in a disastrous defeat, and over 50 per cent casualties for the 34th.

For the next five months the 34th alternated between periods of rest, training, labouring, and service in the line. When the German Army launched its last great offensive in the spring of 1918, the battalion was part of the force deployed to defend the approaches to Amiens around Villers-Brentonneux. It took part in a counter-attack at Hangard Wood on the 30th March, and helped to defeat a major drive on Villers-Bretonneux on the 4th April.

Later in 1918, the 34th also played a role in the Allies own offensive. It took part in the battle of Amiens on the 8th August, during the rapid advance that followed, and in the battle of St Quentin Canal- the operation that breached the Hindenburg Line at the end of September, thus sealing Germany’s defeat. The 34th Battalion disbanded in March 1919.