Why hiding battlecruiser construction is an industrial problem

How could a country secretly build a battlecruiser during the interwar period?

Accumulate components among normal naval stores, conceal the hull as harbour construction, and add the conspicuous turrets and superstructure last. A major naval industrial base would make that easier, but the project would remain slow and difficult to hide.

Secret construction would depend on hiding specialized components within an existing naval industry. Britain, Japan and the United States could accumulate guns, turrets and other equipment among normal stores over a decade; Germany might conceal material retained while deactivating ships. Sweden is also suggested as a possible construction location, although no detailed Swedish scheme is developed. The proposed hull would be built in a secured dock under the cover of harbour work or caisson construction. Heavy machinery already moving around such a site could help disguise equipment installation. Turrets and superstructure would go on last because they would make the hull's military purpose obvious. Even this approach would require slow work and sustained secrecy.