The diplomatic history of Australia encompasses the historical events surrounding Australian foreign relations. Following the global change in the dynamics of international state of affairs in the 20th century, this saw a transition within Australia's diplomatic situation to broaden outside of exclusively commonwealth and western European nations. Its core relationship was with Great Britain until 1941, and with the United States and New Zealand since then as represented by ANZUS. In the 21st century trade has soared with China. However, relations have cycled back and forth from friendly to strained. For recent relations see also Foreign relations of Australia.

1901–1914: Post-Federation years The Department of External Affairs was created upon the federation of the Australian colonies, but largely remained an appendage of the Prime Minister's Department. In the view of early governments, foreign policy meant "relations with London on matters of imperial foreign policy on which Australia might have an interest". Australia's first prime minister Edmund Barton was in favour of a uniform foreign policy for the British Empire, suggesting Australia could have no "foreign policy of its own" but expected that the British government would defer to the Australian perspective for "regional" imperial policy. Barton's successor Alfred Deakin took some of the first steps towards diplomatic independence by dealing directly with the Japanese consul-general, for which he was reminded by the Colonial Office that it "expected Australia to conduct any dealings with a foreign power through London". He also dealt directly with the U.S. consul in Sydney to engineer the visit of the Great White Fleet in 1908. His actions "set a precedent for unilateralism" in foreign policy that was followed by his immediate successors as prime minister, with a continued reliance on the British diplomatic service and policy-making apparatus and no efforts to develop Australian equivalents.

Deakin repeatedly lobbied the British government for greater consultation on imperial foreign policy and suggested the establishment of an imperial department of state to coordinate policy, as part of his broader support for an Imperial Federation. Outside of the prime minister, the Australian High Commissioner to the United Kingdom remained the most significant figure conduit for Australian foreign relations. The significance of the role was emphasised by the fact that its first three appointees (spanning from 1910 to 1927) were former prime ministers.

1914–1931: World War I and aftermath World War I brought about an increase in direct Australian interactions with nations outside the British Empire, prompted by strategic concerns including the fate of German territories captured by Allied troops during the war. Prime Minister Billy Hughes visited the United States in 1918 and "in a series of meetings and speeches, called on the US to cooperate with Australia in ensuring postwar security in the Far East". At the 1919 Paris Peace Conference, Hughes led an Australian section within the British delegation and signed the Treaty of Versailles on behalf of Australia, as with other British dominions. Hughes lobbied powerfully for Australian interests at the conference, including the granting of League of Nations mandates over the former German New Guinea and Nauru and opposition to Japan's Racial Equality Proposal to protect the White Australia policy.

The 1920s marked "the genesis of a distinct Australian foreign policy", largely in response to changing power dynamics in the Pacific following the Washington Naval Conference of 1922 and the subsequent decline in British influence. However, in the short-term Australia continued to rely on "the UK and its imperial machinery for diplomatic representation and economic and material security". Following the 1923 Imperial Conference, attempts to formulate a uniform imperial foreign policy were largely abandoned in favour of a system of dominion ratification of British decisions. Governmental interest in foreign policy declined during the Great Depression as the Scullin government concentrated on internal economic matters. In 1929, internationalist Frederic Eggleston complained to a Senate committee that "no parliament which is responsible for its own foreign policy has less discussion on foreign affairs than does the Australian Parliament".

Trade service and "quasi-diplomatic" appointments The Hughes government sought to establish an independent trade commissioner service, having rejected a previous offer to share the British trade service. Trade and customs minister Jens Jensen's June 1918 report recommended the appointment of trade commissioners in Canada, Japan, Russia, South Africa and the United States, who "would link with but not rely upon the British consular service". However, for post-war budgetary reasons the scheme was significantly scaled back.

While not establishing formal diplomatic relations, Australia made a number of "quasi-diplomatic" appointments in the post-war period, who functioned as official representatives of the Australian government but held no diplomatic rank. These included appointment of Henry Braddon to the United States in 1918 with the title of "commissioner" and the appointment of Clive Voss as "commercial agent" in France in 1919. The American posting endured until 1930, with Herbert Brookes serving as the only "commissioner-general for Australia in the United States" until the position was abolished by the Scullin government for cost reasons.

In 1921, Australia appointed its first official representative in Asia, with the appointment of Edward S. Little as trade commissioner to China, based in Shanghai. Senator Thomas Bakhap undertook a trade mission to China in 1922 at the instigation of Hughes, and in the same year Egbert Sheaf was appointed as a trade commissioner to "the East", based in Singapore. The initial trade commissioner service was partially funded by state governments and ultimately failed due to a lack of support from Prime Minister Stanley Bruce and state premiers.

1930s: Appeasement

During the 1930s, Australian foreign policy was centralised around the fear of war and an eagerness to appease Germany, Japan and Italy. The Australian government gave considerable support to the appeasement policies of the Chamberlain government in London regarding Germany. However, as a consequence of supporting Chamberlain, a number of Australians experienced fear due to Japan's strong military and aggressive foreign policyEric Montgomery Andrews, Isolationism and appeasement in Australia: reactions to the European crises, 1935-1939 (Australian National University Press, 1970) whereas Australia was still an evolving nation to wield any independent force in world affairs in the 1930s.David Samuel Bird, J. A. Lyons, the Tame Tasmanian: Appeasement and Rearmament in Australia, 1932-39 (Australian Scholarly Publishing, 2008)

In 1934, the Lyons government despatched the Australian Eastern Mission to East Asia and South-East Asia, Australia's first diplomatic mission outside of the British Empire. The mission visited seven territories, concentrating on China, Japan and the Dutch East Indies (present-day Indonesia), and has been identified as a milestone in the early development of Australian foreign policy. Latham publicly identified the mission as one of "friendship and goodwill", but also compiled a series of secret reports to cabinet on economic and strategic matters. He "actively sought information about trading opportunities across Asia, entering into frequent and detailed discussions with prime ministers, foreign ministers, premiers and governors about Australia‘s trading and commercial interests, custom duties and tariffs". His recommendations proved influential in the development of the Department of External Affairs as an independent department from the Prime Minister's Department and the appointment of Australia's first diplomats in Asia.

World War II At the beginning of World War II, Australia was part of the commonwealth of the British Empire, and expected the United Kingdom would guarantee its security in any conflict with Japan. On 3 September 1939, Prime Minister Robert Menzies announced, "Great Britain has declared war on Germany, and as a result, Australia is also at war... There can be no doubt that where Great Britain stands, there stand the people of the entire British world". Australia was the first nation to come to Great Britain's aid, sending its combat divisions to fight in the Middle East and North Africa.David Day. Menzies and Churchill at War (1993) pp 1-21

The unprecedented Japanese attack on an American naval base at Pearl Harbor, Hawaii, on 7 December 1941, led to the formal entry of the United States into the war. Japanese attacks continued through Burma, Borneo, the Dutch East Indies (Indonesia) and Malaya. The island of Singapore was strategically crucial for the British defence plan, however it was poorly defended and surrendered to the Japanese on 15 February 1942, with thousands of Australians as prisoners of war. British prime minister Winston Churchill had given priority to the European war and was unable to assist the Australians. Australia Prime Minister John Curtin appealed to the US instead, "Australia looks to America free of any pangs as to our traditional links of kinship with Great Britain." This speech announced the shift of reliance from Great Britain to the United States.

Relations with the United States

In March 1942 after the Japanese attacks on Darwin, U.S. President Roosevelt ordered General Douglas MacArthur to move the American base from the Philippines to Brisbane, Australia. By September 1943, more than 120,000 American soldiers were in Australia. The Americans were warmly welcomed at first but tensions grew evident. MacArthur worked closely with the Australian government and took command of its combat operations. Fighting continued throughout Southeast Asia for the next two years. When the European war was declared over, Australia and the US still had a war to win against Japan. MacArthur promoted a policy of "island hopping" for his American troops while he suggested that the Australian troops should continue clearing and rounding up the Japanese from New Guinea, New Britain, Borneo and Bougainville.

Communism and the Cold War era Although the Union of Soviet Socialist Republics (USSR) and the United States co-operated during World War II, the tensions between the two superpowers over economics (Communism versus capitalism), political authority (totalitarianism versus liberalism) and the fate of Europe (East versus West) escalated into the Cold War by 1947.David McLean, "From British colony to American satellite? Australia and the USA during the cold war." Australian Journal of Politics & History (2006) 52#1 pp: 64-79. Australia unequivocally stood by the American side and the Cold War became the preponderant influence on Australian foreign policy.Peter Geoffrey Edwards and Gregory Pemberton, Crises and Commitments: The Politics and Diplomacy of Australia's Involvement in Southeast Asian Conflicts 1948-1965 (Allen & Unwin in association with the Australian War Memorial, 1992)