Amphibious warfare was critical to the success of Allied forces in the South West Pacific Area (SWPA) during the Pacific War. However, at the beginning of the war both the Australian and United States forces in the SWPA had little knowledge, expertise, or experience in this form of warfare. This article traces the development of amphibious warfare in the SWPA through organization, training, tactics, doctrine, and operations. While focusing on the Australian experience and highlighting the evolution of capabilities between 1942-45 through an analysis of the assaults on Lae (1943) and Balikpapan (1945), it contextualizes this experience within General Douglas MacArthur's maritime strategy and the friction inherent in combined amphibious operations in this theater. The article highlights the evolution of the Australian Army from a force almost totally unfamiliar with the practice of amphibious operations to one which, in combination with its United States coalition partner, becomes a practitioner par excellence in this form of warfare.