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. After investigating the US "TFX", North American A-5 Vigilante and McDonnell Douglas F-4 Phantom II, the British BAC TSR-2, and the French Dassault Mirage IV, Hancock decided the swing-wing TFX, forerunner of the General Dynamics F-111, would be the aircraft best suited for this role. As the TFX had not yet flown, he recommended purchase of the already operational Vigilante to counteract a perceived imminent threat from Indonesia. 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. The same month, as "Konfrontasi" continued to simmer, Hancock approved simplification to the rules of engagement for Australian CAC Sabre fighters based at RAAF Butterworth to engage and destroy Indonesian aircraft violating Malay air space. 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.