He was concerned about German naval activity in the Baltic Sea and initially wanted to send a naval force there but this was soon changed to a plan, codenamed "Operation Wilfred", to mine Norwegian waters and stop iron ore shipments from Narvik to Germany. There were disagreements about mining, both in the war cabinet and with the French government. As a result, "Wilfred" was delayed until 8 April 1940, the day before the German invasion of Norway was launched.