 Complete the following phrase:  Since August 1941, the western Allies had run convoys of ships from the United Kingdom and Iceland to the northern ports of the Soviet Union to provide essential supplies for their war effort on the Eastern Front. These endured much hardship, frequently attacked by German naval and air forces stationed in occupied Norway. A key concern were German Kriegsmarine battleships such as the and Scharnhorst. Even the threat of these ships presence was enough to cause disastrous consequences for the convoys, such as 