The Sydney scenario is built by comparing archival arguments, parliamentary debates, and opposing interpretations rather than granting Britain unlimited money or changing every strategic condition.
Rear Admiral Sir Herbert Richmond's Far Eastern war plan used Singapore as an assembly base before advancing through Hong Kong and Weihaiwei to blockade Japan with submarines and cruisers.
A station-by-station survey shows why Indian, Chinese, and Australian alternatives each carried greater political, geographic, or infrastructure costs than Singapore.
European policy in the region emphasized preserving and consolidating the postwar settlement rather than launching a fresh wave of territorial expansion.
Australia and New Zealand favored renewing the Japanese alliance, while Canada feared its effect on relations with the United States and helped force a British strategic choice.
Japan's capture of German-held Tsingtao, Mediterranean anti-submarine service, and offer of capital ships after Jutland underpinned dominion confidence in the alliance.
Building a Far Eastern base served as visible proof that Britain intended to reinforce Australia and New Zealand rather than leave them strategically isolated.
Parliamentary opposition treated Singapore as an expensive new commitment, while supporters presented it as a long-term logistics hub and guarantee of imperial communications.
Discussion meant retaining Singapore among possible plans, while entertaining it meant moving toward action when the threat, timing, and resources made the proposal viable.
Opponents alleged that Singapore evaded restrictions on Hong Kong, while the wider argument centered on electoral pressure and whether Britain would fund distant security before a crisis.
Many parliamentarians reasoned in European distances, while the Army and RAF treated the Far East as a naval problem because they could not project force across it.
Singapore won on treaty freedom, chokepoint geography, and local subsidies; a Sydney alternative requires Australia to outbid those advantages by funding the base.
Nelson and Rodney were already ordered and laid down by 1922, so the 1924 Sydney divergence affects later ships and refits rather than their basic design.
Moving the theater-entry base from Singapore to Sydney raises the key voyage from about 5,365 to 9,644 nautical miles and forces longer-ranged ships and more fleet oilers.
The 9,644-nautical-mile route from Suez to Sydney creates gaps between fixed bases that must be bridged by more refueling stops and earlier at-sea logistics.
Expanding Garden Island and Cockatoo Island into a fleet hub creates capital-ship repair capacity and a political need to coordinate British and dominion forces under one theater command.
Sydney would gain floating-dock reinforcement, while mobile naval-base units carried repair capacity forward as Britain retook Hong Kong and established itself at Weihaiwei.
RAF staff meant that no strike aircraft were available, while naval officers understood the same message to mean that neither strike aircraft nor fighters could support Force Z.
Protecting both Singapore's chokepoint and Sydney's fleet hub creates continuing demand for 15-inch guns, Australian shell production, and ammunition stockpiles across the Empire.
A senior Far East headquarters in Sydney would require better rail and administrative links with Canberra, making land transport part of the naval-base program.
Turning Sydney into a strategic fleet target brings earlier investment in fighters, warning radar, radar manufacturing, and long-range maritime patrol.
Sydney combines a defensible harbor with existing naval facilities, while Adelaide's extra space does not offset the cost of starting from a weaker base.
A British admiral would lead the theater, but Australian ownership and investment make an Australian deputy more plausible than rotating the post between services.
Japan still strikes Pearl Harbor first, but a Sydney-centered repair and command system can send a balanced carrier task force toward Malaya instead of the historical Force Z.
The scenario's largest consequence is a decade of theater-level coordination that exposes weak plans, aligns the services, and makes Far Eastern defense politically accountable.
British planning treated the Far East as a naval theater, with the RAF and Army supporting the Royal Navy rather than independently owning Malaya's defense.
A senior Far East headquarters could question dispersing Canadian troops to Hong Kong and building more airfields than available aircraft and ground forces could defend.
The Royal Navy still needs a mix of strike and fleet carriers, with treaty tonnage and theater coverage favoring more hulls rather than simply repeating Ark Royal.