The Battle of Fromelles on 19–20 July 1916 was the first occasion on which the First Australian Imperial Force (AIF) saw action on the Western Front. The battle is widely regarded as a disaster for the Allies, and has been described as "the worst 24 hours in Australia's entire history." It resulted from a plan to divert German attention from the Battle of the Somme, but historians estimate that 5,500 Australians and 2,000 British troops were killed or wounded. The Australian losses were equivalent to the combined total Australian losses in the Boer War, Korean War and Vietnam War: although later World War I actions would be more deadly for the AIF, Fromelles was the only one to achieve no success.
Adolf Hitler is believed to have served as a messenger on the German side with the 6th Bavarian Reserve Division.