The Allied Supreme War Council used assistance to Finland during the Winter War as an acceptable rationale for entering Norway. Initial plans centred on a landing at Narvik, whose harbour could support ships and forces while lying beyond the easy reach of aircraft based in Germany. Operation Wilfred would instead mine Norwegian waters, with a wider expeditionary force available to pre-empt German action. Norway still had not mobilised even as both sides discussed intervention. Small standing forces in the major ports could have made an opposed landing much more difficult.
Chapter · 4:36-7:44
Allied intervention plans and Operation Wilfred
Aid to Finland supplied the political case for Allied intervention, while Narvik's position and facilities made it the natural focus of landing and mining plans.