When MacArthur arrived in Australia after evacuating Bataan, he was a General in search of an offensive army. The Americans did not yet have a fighting force in the Pacific, and the Australians were committed in North Africa, enroute to Pacific stations, or in training or garrison in Australia. At one point in early 1942, there were four operational P-40 fighter planes and one B-17 bomber. The only combat-worthy division was Australian, and it was needed to defend Australia, not for offensive operations.
MacArthur was not going to wait for the Japanese to attack Australia. He wanted to use Port Moresby as a base of operations to move up through New Guinea and advance to the Philippines. His problem, besides the Japanese, would be supply. He had to prove that the New Guinea campaign would be the definitive campaign to get back to the Philippines and win the war.
While MacArthur and his staff wanted to return to Manila, not all of the Allies were so inclined. Nimitz favored advancing through the central Pacific, and the British and her Dominions thought Java should be the primary focus. Thus began the Allied interservice rivalry between the Army and the Navy.
MacArthur, for his part, wanted to advance with American forces as soon as he could. In November 1942 he marched unprepared and undersupplied American troops on Buna. They were driven back to the beach, barely holding on to their landing zone. MacArthur’s staff sent glowing communiques claiming advance, and declared Buna secure. While the American public was happy with victory, the Australians were landed to actually take the objective. Buna was declared secure, but fighting continued. The Australian government was privately unhappy with the casualties and with the credit going to the Americans, who would not have succeeded without the Australians. Plus, the Australian public felt the primary goal should be developing a deense in case the Japanese invade Australia.