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In December 1941, Japan launched, in quick succession, attacks on British Malaya, the United States naval base at Pearl Harbor, and Hong Kong. Churchill's reaction to the entry of the United States into the war was that Britain was now assured of victory and the future of the empire was safe, but the manner in which British forces were rapidly defeated in the Far East irreversibly harmed Britain's standing and prestige as an imperial power. Most damaging of all was the fall of Singapore, which had previously been hailed as an impregnable fortress and the eastern equivalent of Gibraltar. The realisation that Britain could not defend its entire empire pushed Australia and New Zealand, which now appeared threatened by Japanese forces, into closer ties with the United States. This resulted in the 1951 ANZUS Pact between Australia, New Zealand and the United States of America.

Which territory had been compared to Gibraltar?
Singapore