The convoy was located by German forces on 1 July, shadowed and attacked. As the close escort and the covering cruiser forces withdrew westwards to intercept the German raiders, the merchant ships were left without escorts. The agreement stated that the Soviet government was responsible for receiving the supplies in Soviet ships at British or American ports.
Since the Soviets did not have enough ships for the quantities of aid, British and American ships began to constitute an increasing proportion of the convoy traffic. The first convoy, Operation Dervish , sailed from the United Kingdom in August , two months after the beginning of Barbarossa. By the spring of , twelve more convoys had made the passage with the loss of only one of the ships.
In , the Kriegsmarine had begun concentrating its strength in Norway in winter, to prevent a British invasion of Norway and to obstruct Allied convoys to the Soviet Union. The battleship Tirpitz was moved to Trondheim in January, where she was joined by the heavy cruiser Admiral Scheer and in March by the heavy cruiser Admiral Hipper. The Germans had bases along the Norwegian coast, which meant, until escort carriers became available, Allied convoys had to be sailed through these areas without adequate defence against aircraft and submarine attack.
The Admiralty issued instructions on 27 June, which allowed the convoy to be turned back, temporarily to shorten the distance to the nearest Allied base.
A decoy convoy was also organised to divert enemy forces, consisting of the First Minelaying Squadron and four colliers, escorted by the light cruisers HMS Sirius and HMS Curacoa , five destroyers and several trawlers. This diversionary force assembled at Scapa Flow for a week, sailing two days after the convoy.
