 Ultimately , the voluntary system of recruitment proved unable to sustain the force structure of the AIF , failing to provide sufficient replacements for the heavy casualties it sustained and requiring a number of units to be disbanded towards the end of the war . In mid @-@ 1918 it was decided to allow the men who had enlisted in 1914 to return to Australia for home leave , further exacerbating the manpower shortage experienced by the Australian Corps . Regardless , by the last year of the war the AIF was a long @-@ serving force — even if it was a citizen army and not a professional one like the pre @-@ war British Army — containing 141 @,@ 557 men with more than two @-@ years service , including , despite the heavy casualties suffered at Gallipoli in 1915 and on the Western Front in 1916 and 1917 , 14 @,@ 653 men who had enlisted in 1914 . Battle hardened and experienced as a result , this fact partially explains the important role the AIF subsequently played in the final defeat of the German Army in 1918 . 
