The plan to attack Narvik and the iron mines

The German war industry depended largely on Swedish iron ore, which transited in winter through the Norwegian port of Narvik and ran along the neutral coast of Norway. Winston Churchill, First Lord of the Admiralty, was convinced that cutting this route would deal a serious blow to the Reich's war effort.

The problem was Norwegian neutrality. To mine the coastal waters or land at Narvik would violate the sovereignty of a neutral country, at the risk of offending opinion and pushing Norway into Germany's arms. But to wait was to let the iron feed the German factories.

Churchill could force the passage: mine the Norwegian waters and prepare a landing at Narvik, in defiance of neutrality. Strictly respect Norwegian neutrality and seek other means of pressure. Or try to obtain Norway's consent, which was unlikely. The risk was of provoking a pre-emptive German reaction in Scandinavia — precisely what Berlin was contemplating on its own side.