Clearing skies over the North Sea last week droned anew with battle planes, and rattled with machine-gun fire. German bombers revived their attacks on Great Britain's trawler and fishing fleets. German reconnaissance planes celebrated Air Marshal Hermann Göring's 47th birthday by appearing over British east-coast headlands, estuaries and cities in numbers that suggested they were preparing the long-awaited mass bombing of British naval bases and supply docks.
Meantime the German Air Force exacted an involuntary tribute from the British. The magnetic-mine-laying campaign of Nazi planes in early December obliged Britain to...