Prewar doctrine grouped merchantmen under escorts, routed them south of the principal submarine danger, and expected French patrol aircraft to bridge the approach to British air cover. The loss of France and Norway transformed the geography and created an air gap that shipborne fighters would have to help close. The Channel barrier and access to southern ports also depended on friendly control of the continental coast. Escort-carrier demand grew from this sudden collapse of the planned air-and-route system rather than from an entirely new wartime idea.
Chapter · 59:06-1:02:42
How the fall of France and Norway broke convoy doctrine
Britain's planned southern convoy route depended on French and British land-based air cover that vanished after 1940.