 Each division comprised three infantry brigades , and each brigade contained four battalions ( later reduced to three in 1918 ) . Australian battalions initially included eight rifle companies ; however , this was reduced to four expanded companies in January 1915 to conform with the organisation of British infantry battalions . A battalion contained about 1 @,@ 000 men . Although the divisional structure evolved over the course of the war , each formation also included a range of combat support and service units , including artillery , machine @-@ gun , mortar , engineer , pioneer , signals , logistic , medical , veterinary and administrative units . By 1918 each brigade also included a light trench mortar battery , while each division included a pioneer battalion , a machine @-@ gun battalion , two field artillery brigades , a divisional trench mortar brigade , four companies of engineers , a divisional signals company , a divisional train consisting of four service corps companies , a salvage company , three field ambulances , a sanitary section and a mobile veterinary section . These changes were reflective of wider organisational adaption , tactical innovation , and the adoption of new weapons and technology that occurred throughout the British Expeditionary Force ( BEF ) . 
