After the outbreak of World War II in September 1939, Emden took part in laying a defensive minefield off the German coast in the North Sea on 3 September, along with several light cruisers and destroyers. The barrier stretched across the German Bight from the coast of the Netherlands to the Jutland peninsula; the purpose of the minefield was to secure the seaward flank of the Westwall. She conducted the operation with the other light cruisers Nürnberg, Leipzig, Köln, and Königsberg and sixteen destroyers.