Throughout the course of the Pacific War, Australian infantry brigades faced monumental challenges in the SWPA, not only from the terrain and from the enemy but also owing to a rapid evolution of tactics and technologies within these intermediate formations. With time and experience, brigades evolved from rudimentary beginnings into expeditionary forces, incorporating hitherto unfamiliar attached elements, support arms and modes of transportation, all while fighting their way across the SWPA. The Australian infantry brigades adapted from formations established on World War I doctrinal, operational and tactical principles into those using more ‘modern’ organisational techniques and structures. Such an analysis must include a brief examination of the state of these formations at the onset of the war in terms of historical legacies, ‘orders of battle’ and to a limited degree the raw material in terms of manpower represented by Australian brigades at this early stage. One particularly important aspect of this analysis is the key transition of several formations between 1942 and 1945 from ‘standard’ Australian infantry brigades to ‘Infantry Brigade Groups (Jungle)’ and finally to ‘Infantry Brigade Groups (Jungle)’ designated as amphibious ‘Assault Brigades’.2