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 Convoy PQ 17 that was scattered and mostly sunk by German forces after false reports of the "Tirpitz" sailing to intercept them. To ward off the threat of Germany's capital ships in the Arctic and to escort convoys with a high level of success, the Royal Navy had to outlay great assets.