Was the territorial sea twelve miles wide in 1940?

Was twelve nautical miles already the accepted limit of territorial waters during the Altmark incident?

No single modern twelve-mile rule applied in 1940; older claims often followed a roughly three-mile cannon-shot limit, and Altmark was inside Norwegian internal waters regardless.

The modern twelve-nautical-mile territorial sea was formalized much later, while an older cannon-shot tradition often supported a roughly three-mile claim. States varied and some claimed farther limits, so a single modern number should not be imposed on 1940. Jossingfjord lay inside Norway's internal waters, well within any plausible territorial limit. Vian's boarding therefore breached Norwegian neutrality even though Altmark's carriage of prisoners gave Britain a reason to challenge the ship's protected status.