 Williams spent much of 1923 in England, attending the British Army Staff College in Camberley and RAF Staff College, Andover, followed by further study in Canada and the United States the following year. Goble served as Chief of the Air Staff in his absence. Shortly after his return in February 1925, Williams scuppered a plan by Goble to establish a small seaplane base at Rushcutters Bay in Sydney, instead organising purchase of Supermarine Seagulls, the RAAF's first amphibious aircraft, to be based at Richmond. He was promoted to group captain in July and later that year drafted a major air warfare study, "Memorandum Regarding the Air Defence of Australia". Considered prescient in many ways, it treated World War I ally Japan as Australia's main military threat, and advocated inter-service co-operation while maintaining that none of the armed forces was "purely auxiliary to another". Its concepts continue to influence RAAF strategy.
