 This brought him firmly into the inner ranks of the Liberal Party, and in terms of cabinet rank placed him among the party's most senior figures in New South Wales.McMahon oversaw the creation and administration of what became the "National Service Act 1964", which re-introduced compulsory conscription for 20-year-old males in anticipation of further Australian involvement in South-East Asia.On the labour side of his portfolio, he frequently came into conflict with the leadership of the Australian Council of Trade Unions (ACTU), though there was no major industrial action during his tenure.