The pre-war plan assumed friendly France and placed a mined, patrolled barrier across the Channel's North Sea entrance so troops on the continent could be supplied. France's fall reversed the geography and left Scharnhorst and Gneisenau on an Atlantic coast from which they might break out against shipping. From the British perspective, either outcome of the Channel Dash removed an immediate problem: sinking the ships would destroy them, while their return to Germany moved them away from the Atlantic. The ships in the North Sea entered a defensive problem anticipated in pre-war planning. Their possible breakout from French Atlantic ports had been the more dangerous scenario.
Chapter · 24:19-27:25
The Channel Dash and Britain's strategic geography
Pre-war Channel defence expected a mine barrier and patrols to support Britain in France; after France fell, the Channel Dash changed the problem but also moved German capital ships away from the Atlantic.