In the summer of 1940, Nazi Germany's occupation of Norway brought to the fore the need to transfer troops and munitions not only by sea, but also through the neutral countries of Sweden and Finland.
The German transfer rights were in breach of, if not the letter, then the spirit of the Russo-Finnish Moscow Peace Treaty, as well as the Russo-German Molotov-Ribbentrop Pact, but the Finns greeted the agreement as a balance against the increasing pressure from the Soviet Union.