In the case of Norway, the 1940 German invasion of Norway in the 1946 Nuremberg trials the German defense argued that Germany was "compelled to attack Norway by the need to forestall an Allied invasion and that her action was therefore preemptive."[16] The German defence was referring to Plan R 4 and its predecessors. Norway was vital to Germany as a transport route for iron ore from Sweden, a supply that Britain was determined to stop.