Even after the tremendous efforts of World War II, Army activity continued at a high level for several years. Following agreement reached within the British Commonwealth and with the United States, a British Commonwealth Occupation Force (BCOF), comprising Australian, British, Indian and New Zealand formations, was raised and deployed to participate in the occupation of the defeated Japan. Its main tasks were demilitarisation and demobilisation, as well as enforcing military government regulations. Because of the Australian commitment in the Pacific theatre of the war, the appointment of GOC BCOF was filled by Australian Army officers. 

• The Australian Army’s contribution was the 
  • 34th Infantry Brigade (three battalions - 65th, 66th and 67th). 
    • This formation was raised at Morotai, and drawn from infantry units spread across the South West Pacific Area at the cessation of hostilities. 
  • An armoured car squadron and a
  •  general hospital, along with other smaller units, were also contributed

Two years later the bulk of the Commonwealth’s Forces had been withdrawn, but Australia still maintained her presence in Japan. The three battalions of 34th Infantry Brigade were the nucleus of the post-war Regular Army and were designated 1st, 2nd and 3rd Battalions of the Australian Regiment in 1948, and the Royal Australian Regiment (RAR) in the following year. Of the original three battalions, only the 3rd Battalion (3RAR) remained in Japan. A 4th Battalion, (4RAR), was raised in Australia as a depot battalion in 1952 but disbanded at the end of the decade. The occupation of Japan ended with the signing of the Treaty of San Francisco in September 1951.

To augment the Regular Army of 19,000, the field force component of which was a regular brigade group plus an armoured element, the Citizen Military Forces (CMF ).were re-raised in 1948. The CMF was to comprise two infantry divisions and other units, to a strength of 50,000. However by 1949-50 the CMF strength was only some 23,000.

Meanwhile, in 1947, the Australian Army's involvement in multinational peacekeeping had commenced, with the contribution of military observers to what was (initially) titled the United Nations Good Offices Commission (GOC). The Commission was tasked with delineating and supervising the ceasefire between the Netherlands forces trying to re-establish Dutch rule in the East Indies and Indonesian forces fighting for the independence of their new republic. The GOC was later retitled the United Nations Commission for Indonesia (UNCI). Its task ended in 1951. The Australian Army also contributed observers to the UN Military Observer Group in India and Pakistan (UNMOGIP) from 1950 until 1985, and one observer to the UN Commission on Korea (UNCOK) in 1950, although this commitment ceased with the outbreak of the war in Korea in the same year.

In mid-1949, the New South Wales and Queensland coal strike, inspired by militants within the miners' union, saw the federal government move troops into the mines to maintain production. The strike came to an end in August because the railways unions decided to move the coal mined by the Army, leaving the mining union isolated within the trade union movement.

In December 1949 a new government was elected, based broadly on a policy aimed at reducing communist influence at home and its further spread through South East Asia. To achieve this aim it appeared necessary to maintain the confidence of nations in the area against external pressure, to encourage regional security and develop local regional, as well as Australia's, defence capacity. The Government, believing that the army structure was inadequate for this task, introduced the National Service Act in 1951. The Act provided for the compulsory call-up of all 18 year old males, with an obligation to serve 176 days, 98 of which were to be full-time. As a result, by 1956, the CMF strength had reached over 87,000

Regional Security 1951 - 55

Meanwhile Australia had been seeking a 'more comprehensive system of regional security in the Pacific area'. To a degree this was met by the Australian, New Zealand and United States Treaty (ANZUS), which was signed in September 1951.  A further step towards regional security was the signing of the South-east Asia Collective Defence Treaty by the United States, Australia, New Zealand, France, Britain, Pakistan, Thailand and the Philippines in September 1954. This treaty resulted in the South East Asia Treaty Organisation (SEATO). Any attack on a member state, or on protocol states (South Vietnam, Laos and Cambodia ).was designated a matter of common danger inviting a common response, although the United States specified that the treaty could only be invoked in relation to a communist attack.

A more localised security arrangement for Australian, New Zealand and British interests was ANZAM (Britain being the governing power of what was then the Federation of Malaya). In 1955, the British Commonwealth Far East Strategic Reserve (BCFESR ).was formed in Malaya. The Australian Army component was mainly a battalion group, based on an RAR battalion, forming part of 28 Commonwealth Brigade Group.

The primary role of the BCFESR was 'to provide a deterrent to, and be available at short notice to assist in countering, further communist aggression in South East Asia'. Its secondary and related role was to assist in the maintenance of the security of Malaya by participating in operations against Communist Terrorists (CT). A communist insurrection to seize control of Malaya had commenced in 1948 and became the Malayan Emergency

The Pentropic Organisation 1960-65

With the end of the National Service scheme in November 1959, came the desire to modernise the Army and restructure it to enable better integration in operations with the forces of Australia's main ally, the United States. As a result, the Army was reorganised on a new divisional structure, called the Pentropic Division. The US Army had experimented with a Pentropic Divisional structure, based on five battle groups. The core element of each was a significantly enlarged infantry battalion, to which was added elements of supporting arms. This organisation, which was the blue print for the Pentropic arrangement, eliminated the intermediate-level brigade headquarters. Implementation of the Pentropic divisional structure commenced in 1960.

The restructuring of the Army, particularly the CMF infantry battalions, to form the new battle groups, involved the disbanding of many old units with historical links going back to the Sudan, South Africa and the two World Wars, as well as severing traditional ties with their local communities. The new organisation presented a complex command and staff organisation as well as a number of difficulties at lower levels. The US Army abandoned its experiment in 1961, however the Australian Army persevered with the Pentropic structure until November 1964.

One significant complication was the requirement to maintain an RAR battalion with the BCFESR in Malaya (Malaysia after 1963) on the standard British Commonwealth battalion structure, whilst all other battalions were on the enlarged Pentropic structure. This resulted in battalions having to be reorganised for service in BCFESR. Reversion to the previous Tropical Warfare divisional - and battalion - structure was effected in 1965, with some restoration of the old identities of the original CMF battalions