Failure in France produced a concrete change in British defensive planning. An initial scheme tried to create a solid coastal crust, spreading strength around every possible landing place. Brooke instead favored a thin delaying screen backed by large mobile forces that could move against the actual attack. The arrangement accepted that the defender could not be equally strong everywhere and preserved mass for the decisive point. The lesson from France therefore changed the disposition of forces assigned to defend Britain.
Notable Point · 1:30:36-1:31:27
Brooke applies France's defence-in-depth lesson
When defending Britain, Alan Brooke rejected an evenly strong coastal crust and kept mobile strength in depth to counter whichever landing actually developed.