Norwegian control opened a reliable North Sea route

French Atlantic ports were valuable only if Germany could move personnel and equipment to them and send ships safely to sea. The English Channel offered a possible route, but minefields, anti-submarine patrols, convoys, and coastal batteries made repeated passage hazardous. Control of Norway created a more reliable path up the North Sea and along the Norwegian coast before turning into the Atlantic. Ships could use that route for an operation and then return to France, making geography and transit security as important as possession of the French bases themselves.