What Germany needed for a credible surface-raiding threat

How large would the Kriegsmarine need to be to tie down substantial Royal Navy resources?

Roughly four or five battleships, at least two carriers, and enough cruisers and destroyers to form a self-sufficient Atlantic task group.

Germany needed roughly four or five operational battleships, at least two carriers, and a substantial cruiser and destroyer screen to create the required burden. Those ships had to deploy together as a self-sufficient task group into the North Sea and Atlantic. The Royal Navy would then need a comparable group ready to intercept it at short notice. Historical Germany never achieved that concentration, which left Britain freer to distribute major units across the Mediterranean, Pacific, and other global commitments.