A Sydney strike and British imperial overstretch

Australia and New Zealand had regarded Japan as a primary security concern and had been less eager than Canada to end the Anglo-Japanese alliance. A strike on Sydney would validate those fears and compel Britain to redistribute ships and attention while already fighting Germany and Italy. London would face pressure to reinforce Australia, Singapore, and the wider imperial position at the expense of the Atlantic or Mediterranean. That diversion could leave Brunei and the Dutch East Indies more exposed to later Japanese moves while still denying Washington a direct Japanese attack.