The
First Australian Imperial Force (
1st AIF) was the main
expeditionary force of the
Australian Army during
World War I. It was formed on 15 August 1914, following
Britain's declaration of war on
Germany, initially with a strength of one infantry
division and one
light horse brigade. The infantry division subsequently fought at
Gallipoli between April and December 1915, being reinforced by a second division which was later raised, as well as three light horse brigades. After being evacuated to Egypt the AIF was expanded to five infantry divisions, which were committed to the fighting in France and Belgium along the
Western Front in March 1916. A sixth infantry division was partially raised in 1917 in the United Kingdom, but was broken up and used as reinforcements following heavy casualties on the Western Front. Meanwhile, two mounted divisions remained in the Middle East to fight against Turkish forces in
the Sinai and Palestine.