In June 1916, the battalion was transferred to the European theatre along with the other battalions of the four Australian infantry divisions that were in the Middle East at that time and they arrived in France at the end of the month. Following this, the 55th Battalion took its place in the trenches along the Western Front in mid-July, amidst heavy fighting on the Somme. The battalion did not have to wait long before they experienced their first engagement of the campaign, being committed to the Battle of Fromelles a week later on 19 July. Initially they were placed in reserve, but as the attack stalled, the 55th Battalion was tasked with providing the rearguard for the withdrawal of the assault formations. After spending the winter in the trenches on the Somme, in 1917 they took part in the advance to the Hindenburg Line that followed the German withdrawal that had been affected as part of a German plan to shorten their lines and free up reserves. The battalion then played a defensive role in the Second Battle of Bullecourt before moving to Ypres in Belgium where they took part in the Battle of Polygon Wood on 26 September 1917.