Initially repelled by the British Navy, Hitler's invasion of France serves as a diversion allowing German forces to conquer Norway. By holding Narvik in the far north Germany is assured of a reliable source of iron ore. Holding Norway also offers the opportunity to seize the part of Murmansk and cut the allied supply line to Russia. But what is conquered must then be defended which means the construction and manning of extensive defenses diverting critical resources from the Eastern Front.
—David Foss