Lend-lease The Soviet leaders needed to replace the colossal losses of military equipment lost after the
German invasion, especially when Soviet war industries were being moved out of the war zone and emphasised tank and aircraft deliveries. Machine tools, steel and aluminium was needed to replace indigenous resources lost in the invasion. The pressure on the civilian sector of the economy needed to be limited by food deliveries. The Soviets wanted to concentrate the resources that remained on items that the Soviet war economy that had the greatest comparative advantage over the German economy. Aluminium imports allowed aircraft production to a far greater extent than would have been possible using local sources and tank production was emphasised at the expense of lorries and food supplies were squeezed by reliance on what could be obtained from lend–lease. At the Moscow Conference, it was acknowledged that 1.5 million tons of shipping was needed to transport the supplies of the First Protocol and that Soviet sources could provide less than 10 per cent of the carrying capacity. The British and Americans accepted that the onus was on them to find most of the shipping, despite their commitments in other theatres. The Prime Minister,
Winston Churchill, made a commitment to send a convoy to the Arctic ports of the USSR every ten days and to deliver a month from July 1942 to January 1943, followed by and another more than already promised. In November, the US president,
Franklin D. Roosevelt, ordered Admiral
Emory Land of the US Maritime Commission and then the head of the
War Shipping Administration that deliveries to Russia should only be limited by 'insurmountable difficulties'. The first convoy was due at Murmansk around 12 October and the next convoy was to depart Iceland on 22 October. A motley of British, Allied and neutral shipping loaded with military stores and raw materials for the Soviet war effort would be assembled at
Hvalfjörður in Iceland, convenient for ships from both sides of the Atlantic. From
Operation Dervish to
Convoy PQ 11, the supplies to the USSR were mostly British, in British ships defended by the Royal Navy. A fighter force that could defend Murmansk was delivered that protected the Arctic ports and railways into the hinterland. Before September 1941 the British had dispatched 450 aircraft, of rubber, 3,000,000 pairs of boots and stocks of tin, aluminium, jute, lead and wool. In September British and US representatives travelled to Moscow to study Soviet requirements and their ability to meet them. The representatives of the three countries drew up a protocol in October 1941 to last until June 1942. British supplied aircraft and tanks reinforced the Russian defences of Leningrad and Moscow from December 1941. The tanks and aircraft did not save Moscow but were important in the Soviet counter-offensive. The was by then reduced to 600 operational aircraft on the Eastern Front, to an extent a consequence of being sent to the Mediterranean against the British. Tanks and aircraft supplied by the British helped the Soviet counter-offensive force back the Germans further than might have been possible. In January and February 1941, deliveries of tanks and aircraft allowed the Russians to have a margin of safety should the Germans attempt to counter-attack.
Signals intelligence Ultra The British
Government Code and Cypher School (GC&CS) based at
Bletchley Park housed a small industry of code-breakers and
traffic analysts. By June 1941, the German
Enigma machine Home Waters () settings used by surface ships and U-boats could quickly be read. On 1 February 1942, the Enigma machines used in U-boats in the Atlantic and Mediterranean were changed but German ships and the U-boats in Arctic waters continued with the older
Home from 1942,
Dolphin to the British). By mid-1941, British
Y-stations were able to receive and read
W/T transmissions and give advance warning of operations. In 1941, naval
Headache personnel with receivers to eavesdrop on wireless transmissions were embarked on warships. ====== The rival German (, Observation Service) of the (MND, Naval Intelligence Service) had broken several Admiralty codes and cyphers by 1939, which were used to help ships elude British forces and provide opportunities for surprise attacks. From June to August 1940, six British submarines were sunk in the
Skaggerak using information gleaned from British wireless signals. In 1941, read signals from the Commander in Chief Western Approaches informing convoys of areas patrolled by U-boats, enabling the submarines to move into "safe" zones.
Arctic Ocean Between Greenland and Norway are some of the most stormy waters of the world's oceans, of water under gales full of snow, sleet and hail. The cold Arctic water was met by the
Gulf Stream, warm water from the
Gulf of Mexico, which became the
North Atlantic Drift. Arriving at the south-west of England the drift moves between Scotland and Iceland; north of Norway the drift splits. One stream bears north of
Bear Island to
Svalbard and a southern stream follows the coast of Murmansk into the Barents Sea. The mingling of cold Arctic water and warmer water of higher salinity generates thick banks of fog for convoys to hide in but the waters drastically reduced the effectiveness of
ASDIC as U-boats moved in waters of differing temperatures and density. In winter, polar ice can form as far south as off the North Cape and in summer it can recede to Svalbard. The area is in perpetual darkness in winter and permanent daylight in the summer and can make air reconnaissance almost impossible. Around the
North Cape and in the
Barents Sea the sea temperature rarely rises about and a man in the water will die unless rescued immediately. The cold water and air makes spray freeze on the superstructure of ships, which has to be removed quickly to avoid the ship becoming top-heavy. Conditions in U-boats were, if anything, worse the boats having to submerge in warmer water to rid the superstructure of ice. Crewmen on watch were exposed to the elements, oil lost its viscosity and nuts froze and sheared off bolts. Heaters in the hull were too demanding of current and could not be run continuously. ==Prelude==