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After the Japanese occupation of New Guinea, they were ready to attack Australia, which was in danger of being overrun by the Japanese until the end of 1942. Some Australian military personnel even predicted that due to insufficient troops, Australia could only resist for a maximum of 6 weeks before having to lay down its arms and surrender.
The main force of the Australian Army, the Second Army Division
In order to show allegiance to Britain and win the protection that Britain may provide in the future, more than 20,000 people from the Second Army Division, the main force of the Australian army, were sent to the Middle East in the early days of World War II to assist Britain in resisting the attacks of Italy and Germany and defend British hegemony and interests in the Middle East. After the Japanese captured Papua New Guinea, they launched a tentative attack on Australia, which greatly alarmed the Australian government and people.
The Australian government and military, as well as the public at large, recognized that Australia's immediate priority was to strengthen its homeland security, rather than sending its own limited military forces thousands of miles away to fight for British interests in Europe or the Middle East, which had nothing to do with its own interests. Under the dual pressure of the people and the Japanese invasion, the extremely frightened Prime Minister Curtin sent a telegram to British Prime Minister Winston Churchill, demanding that all Australian troops that were following Britain in the Middle East be immediately transferred back for the defense of the Australian homeland. However, Churchill, out of Britain's own interests, resolutely did not allow the Australian army to return to defend his country, and the British and Australian sides quarreled fiercely.
In Churchill's eyes, Europe and the Middle East were vital to the survival of the British Empire, and how could Australia, thousands of miles away, be compared with Britain's hegemonic interests? Prime Minister Winston Churchill then flatly rejected Curtin's request. The indifference of Churchill and the British government to the life and death of Australia fully exposed the extreme selfishness of the old imperialist Britain, and was also mean to Australia, which had always been docile and obedient and sacrificed more than 60,000 people in the First World War for British interests.
After Churchill's refusal, Prime Minister Curtin was extremely angry but helpless, and Australian politicians and people who heard about it were also chilled. The Australian government and ordinary people are very unhappy with Britain's approach to its own interests and ignores Australia's survival. At a critical moment when their country was facing a Japanese invasion, the Australian government did not have the right to move its troops home, which made the Australian government and people extremely indignant against Britain. The rift between Britain and Australia widened, and Australia's determination to turn to the United States has since become stronger. After the Battle of the Philippines, MacArthur led the remnants of American troops to Australia.
This made Australia overjoyed at a critical time. Curtin warmly welcomed the arrival of MacArthur's defeated American army, because the arrival of American troops could not only strengthen Australia's defense force, jointly keep the Japanese army out of Australia, but also further strengthen political and military relations with the United States. President Roosevelt was also acutely aware of Australia's strategic importance to the Pacific War after the defeat of American troops from the Philippines.
Japanese forces occupy the Philippines and the Dutch East Indies
After the Japanese occupation of the Philippines and the Dutch East Indies, Australia became the only military base in the southwest Pacific that could be used by the United States as a future counterattack against the Japanese army, which highlighted Australia's military strategic significance to the United States and greatly enhanced Australia's voice in Australia-US relations. President Roosevelt's attitude toward military aid to Australia and joint efforts to prevent the Japanese from conquering the Australian mainland changed significantly. He assured Curtin that the United States would do everything in its power to block the Japanese attack and never let Australia fall into Japanese hands.
After hearing President Roosevelt's assurances, Prime Minister Curtin and the Australian people knew that the protection they had longed for for America had finally arrived! Australian military and political officials are also optimistic that Australia's military alliance with the United States will follow. MacArthur's defeat in Australia provided an opportunity for Australia to forge close relations and establish military alliances with both the political and military circles of the United States. Curtin suggested that President Roosevelt establish a Southwest Pacific Theater Command in Australia to command the U.S. and Australian forces. Curtin also expressed his willingness to hand over the command of the Australian army to the American generals, and promised that all Australian troops would be under the command of the American generals.
After President Roosevelt appointed MacArthur as the commander-in-chief of the allied forces in Australia, Curtin did not dislike MacArthur as a defeated general, but handed over the command of the Australian army to MacArthur on behalf of the Australian government, who had full command of the US-Australian coalition. This was the first time that Australia had handed over military command to a U.S. general, and Australia had always given command of the Australian military to a British general. This marked that in the face of a major Japanese invasion, the Australian government had to accept geopolitical realities and show heartfelt obedience to the United States.
However, Australian politicians, the military and ordinary people are not saddened by the change of court, but are sincerely happy that their country can form a military alliance with the more powerful United States. It was at this time that the opening song of Radio Australia was no longer "British Bombardier March", but "Go On, Beautiful Australia". Judging from the operational plans of the Japanese army captured after World War II, the Japanese high command did plan to launch a war of aggression against Australia in February and March 1942 to seize the Australian mainland.
Fortunately, most of the Japanese forces were trapped in the Chinese battlefield at that time, and it was simply impossible to concentrate enough troops from China to attack Australia. The Japanese high command estimated at the time that the invasion of Australia would require at least 60,000 combat troops. If it is less than this force, the invasion of Australia will most likely turn into a war of attrition, trapping the Japanese army in it like a Chinese mainland battlefield. The protracted war on the Chinese battlefield was like a nightmare for the Japanese army, and the Japanese high command expected that the Japanese army would not be able to withstand another protracted war of similar Chinese mainland.
Abandon the operational plan for a full-scale invasion of Australia
If Australia also becomes a protracted war, Japan is doomed to become the loser of World War II. Due to the lack of troops, the Japanese high command had to abandon the battle plan of a full-scale invasion of Australia, and instead imposed a siege and blockade on it, cutting off Australia's ties with the outside world, especially the United States, in an attempt to force Australia to surrender. This plan of the Japanese army is obviously unrealistic fantasy, because Australia faces the sea on all sides, and the Japanese army simply does not have enough naval power to surround Australia and completely cut off its maritime links with the outside world, especially the United States.
The Japanese eventually abandoned their plan of attacking Australia, which was fortunate enough to escape the ravages of the Japanese due to the lack of Japanese forces. In early May 1942, the United States launched an attack on Japanese forces stationed in Port Moresby, Papua New Guinea, which was the first confrontation between the main naval forces of the United States and Japan in the Pacific theater, and the famous Battle of the Coral Sea began. Although the two sides suffered equal losses in this battle, the Americans blocked the Japanese army's continued southward advance, which was undoubtedly a strategic victory for the American army. On June 3, the Japanese launched the Battle of Midway in an attempt to annihilate the main U.S. naval forces in the Pacific.
However, the result of this naval battle was another crushing defeat for the Japanese, and the Japanese army had to turn to strategic defense after this naval battle. Faced with two successive strategic defeats, Japan was eager to regain the initiative in the Pacific War and consolidate its hegemony in the Pacific region. The Japanese therefore planned to seize the islands in the southwest Pacific and cut off the military and strategic links between the US Pacific naval and air base Hawaii and the Australian mainland, so that the US military could not use Australia as a military base for future counterattacks.
The Pacific War fully demonstrated the importance of the Pacific Islands region to the military power to establish Pacific hegemony, which also made the Pacific Islands region a region that the United States and Australia must firmly control after World War II. The Australian government and military also had the idea of turning the entire Pacific Islands region into Australia's "backyard" at this time. In order to regain the initiative in the Pacific War, the Japanese tried to reoccupy Port Moresby in Papua New Guinea. In addition, the eastern part of the Pacific Ocean is connected, and the Pacific Ocean can be cut into two sections; The western part of Southeast Asia is of great strategic importance.
After a month of desperate fighting, the Australian army paid a heavy price to block the Japanese attack. The battle was the first land victory of the Allies in the Pacific War, frustrating Japan's strategic attempts. As the Japanese attacked, the U.S. military was also plotting a military counteroffensive. In order to ensure that the strategic link with Australia was not cut off by the Japanese and to ensure the security of Australia, which the US military used as a base for strategic counteroffensives, the US military launched the battle to seize Guadalcanal in the Solomon Islands. Under the heavy fire of the United States, the Japanese had to withdraw from Guadalcanal in early February 1943.
After that, the Japanese launched several counter-offensives in an attempt to retake the island, but all of them failed. During the six-month battle for Guadalcanal, the United States and Japan fought nearly 100 large and small naval battles. The US-led Allied forces have invested 60,000 troops in the battle, with more than 5,000 casualties. The Japanese army committed more than 35,000 combat troops and suffered nearly 25,000 casualties  . The Battle of Midway and the Battle of Guadalcanal were turning points in the Pacific War, when the Japanese completely lost their superiority in the Pacific. The Allies, on the other hand, regained the strategic initiative and reversed the passivity of the early stages of the war.
These victories were followed by strategic offensives against other islands in the Pacific Islands region, such as Bougainville in Papua New Guinea. In February 1944, U.S. forces captured most of the islands in the Marshall Islands. This was followed by a landing on the Bismarck Islands, completing the siege of the Japanese military fortress of Rabaul. The U.S. Army then launched the Campaign of New Guinea, which basically recovered the entire island of New Guinea. In November 1943, the U.S. military launched the Battle of the Gilbert Islands, occupying Tarawa and other islands. In January-February 1944, the U.S. military captured the atolls of Kwajalein, Roy Island-Namur and Enivitok, creating conditions for the capture of the Mariana Islands.
 G.P.Taylor，“New Zealand，the Anglo-apaneseAlliance and the 1908 Visit of the American Fleet”，Australian Journal of Politics & History，Vol.15，Issue1，1969，pp.55-76.
 Joanne Wallis，“Hollow Hehemon：Australia'sDeclining Influence in the Pacific”，Diplomat，21September 2016.
 Nagata Yuriko，“The Japanese in Torres Strait”，AnnaShnukal，Ramsay Guy and Nagata Yuriko（eds.），Navigating Boundaries：The Asian Diaspora in TorresStrait，Canberra，Pandanus Books，2004，pp.138-159.Kate Bagnall，A Legacy of White Australia：Recordsabout Chinese Australians in the National Archives，2018，http：//naa.gov.au/collection/publications.