Holding Narvik reshapes both Arctic and Atlantic convoy warfare

How would Britain holding Narvik in 1940 change the Arctic convoys?

It would reduce German northern air and surface threats and alter U-boat and convoy routes, provided the Allies could keep Narvik supplied, defended, and covered from the air.

If Britain and Norway held Narvik, German aircraft and surface ships would lose much of their northern base network, easing Arctic convoy operations. German submarines and raiders would also lose the most sheltered route along the Norwegian coast, encouraging Atlantic convoys to run farther north and forcing U-boats toward longer approaches from French bases. Holding the port would still demand fighter cover, fuel, continuous seaborne supply, and ground defence along a limited land approach. Narvik would not automatically become a quick springboard for liberating all Norway, but a force led by experienced Norwegian and British commanders could remain a persistent threat on Germany's northern flank.