In his role as the Air Force's senior officer, Hancock initiated redevelopment of RAAF Base Learmonth in north Western Australia, as part of a chain of forward airfields for the defence of the continent.

He also evaluated potential replacements for the RAAF's English Electric Canberra bomber, finding the American "TFX" (later the General Dynamics F-111) to be the most suitable for Australia's needs, though he did not recommend its immediate purchase due to its early stage of development.

[3][6] His preferred career path in the military was engineering, and it was only when he found there was no vacancy in his corps of choice, and that he had instead been earmarked for the artillery, that he put his name forward for transfer to the Royal Australian Air Force (RAAF).

[1] It was common practice for Duntroon graduates to be given positions in the Air Force because of their training in administration, and Hancock spent most of the 1930s in a succession of posts at RAAF Headquarters in Melbourne.

[17] As Director, Hancock was responsible for surveying and developing a military aerodrome at Evans Head, near the Queensland and New South Wales border, that became home to No.

[24] He relinquished his acting rank on 12 January,[25] and became Assistant Director of Plans at Allied Air Forces Headquarters, South West Pacific Area that April.

Providing close air support to Australian ground troops in the lead-up to the final assault on Wewak, the wing flew over 1,400 sorties and dropped more than 1,200 tons of bombs in May alone.

By mid-year, Hancock's forces were acutely short of fuel and ordnance, to the extent that his squadrons took to arming their Beauforts with captured Japanese bombs.

71 Wing was active to the last day of the Pacific War, flying its final combat mission involving thirty Beauforts only hours before news of victory arrived on 15 August 1945.

[32][33] Among a small coterie of wartime RAAF commanders considered suitable for future senior roles, Hancock retained his rank of group captain following the end of hostilities.

[7][41] Departing in late 1949, he spent the following year in Britain, where he attended the Imperial Defence College, receiving a promotion to substantive air commodore on 1 February 1950.

[7][47] He spent much of the latter half of 1955 and early 1956 laid low by a stomach ailment that was initially diagnosed as amoebic dysentery but later thought to be Malta fever or malaria.

[36][52] According to the official post-war history of the RAAF, though fastidious in appearance and a strict teetotaller, Hancock was known for his enthusiasm in meeting staff and as "an indefatigable participant in mess functions and games".

[57] As CAS, Hancock worked to enhance the RAAF's deterrent capability in the Pacific region, particularly in light of heightened tensions with Indonesia during its period of Konfrontasi with Malaysia.

In June 1963, Hancock undertook a mission to Britain, France and the United States to consider potential replacements for the English Electric Canberra bomber as Australia's prime aerial strike platform.

In the event, the Federal Government did not go ahead with an immediate replacement for the Canberra, and Hancock's original choice of the TFX was taken up as a long-term solution, leading to Australia's agreement in October to purchase the F-111C.

[59] The following month he urged using RAAF Canberras from Butterworth to make pre-emptive strikes against Indonesian air bases, in retaliation for incursions into West Malaysia, but Britain, which had initially requested Australia's involvement, held back on action.

In this, he continued a policy initiated by his predecessor as CAS, Air Marshal Scherger, of developing a chain of so-called "bare bases" in Northern Australia.

Flying out of this airfield, the F-111s could destroy "vital centres in Java"; just as importantly for deterrence purposes, Hancock contended, enhancing the base's capability would send a clear message to Indonesia's hierarchy.

Though the project was delayed, in part due to thawing in relations between Australia and Indonesia, Learmonth's upgrade was completed in 1973, the same year the F-111 finally entered RAAF service.

By mid-1964, the Commonwealth had already sent a small team of military advisors, plus a detachment of newly acquired DHC-4 Caribou cargo planes, to the region at the request of the South Vietnamese government.

Hancock proposed that Australia continue to command the facility and provide local air defence, though this effectively made the Sabres a support unit in the war effort and therefore potential targets of North Vietnamese attack; as it happened, none occurred.

[7] Later the same year, Hancock took over as Commissioner-General for Australia at Expo 67 in Montreal, Canada, following the sudden death of the previous appointee, Vice Admiral Sir Hastings Harrington.