Operation Gearbox II (17 September 1942 – 7 September 1943) was a Norwegian and British operation during the Second World War on the Arctic island of Spitsbergen in the Svalbard Archipelago. Operation Fritham, the first attempt to establish a base had been defeated when the two ships carrying the force were sunk by bombers on 14 May.
In Operation Gearbox (30 June – 17 September 1942), 57 Norwegian reinforcements with of supplies had arrived by cruiser on 2 July. The reinforcements consolidated the defences of the former settlement at Barentsburg and made preparations for Gearbox II, another reinforcement of the Norwegians and part of the plan for Convoy PQ 18, to prevent a repeat of Convoy PQ 17 (27 June – 10 July 1942) in which 24 of the 35 freighters in the convoy had been sunk.
Force P (the Spitsbergen Fuelling Force) comprising the fleet oilers and and four destroyer escorts, sailed from Scapa Flow on 3 September and anchored in Lowe Sound (Van Mijenfjorden) several days later. From 9 to 13 September, relays of destroyers were detached from PQ 18 to refuel before the convoy passed (Bear Island), into range of bombers and torpedo-bombers based in north Norway.
After another German weather party was chased off the island by the Norwegians in June 1943, a German flotilla, including , raided Spitsbergen in Operation Zitronella on 7 September, took 31 prisoners and destroyed much of the infrastructure and equipment of Gearbox II. On 19 October, the cruiser and four destroyers delivered more Norwegian troops.
Background
Svalbard
The Svalbard Archipelago is in the Arctic Ocean, from the North Pole. The islands are mountainous with permanently snow-covered peaks, some glaciated; there are occasional river terraces at the bottom of steep valleys and some coastal plains. In winter, the islands are covered in snow and the bays ice over. Spitsbergen Island has several large fiords along its west coast and Isfjorden is up to wide. The Gulf Stream warms the waters and the sea is ice-free during the summer. Settlements were established at Longyearbyen and Barentsburg in inlets along the south shore of Isfjorden, in Kings Bay (Quade Hock) further north along the coast and in Van Mijenfjorden (Lowe Sound) to the south. The settlements attracted colonists of different nationalities and the Svalbard Treaty of 1920 neutralised the islands and recognised the mineral and fishing rights of the participating countries. Before 1939, the population consisted of about 3,000, mostly Norwegian and Russian, people who worked in the mining industry. Drift mines were linked to the shore by overhead cable tracks or rails and coal dumped over the winter was collected by ship after the summer thaw. By 1939, production was about a year, split between Norway and Russia.
Signals intelligence
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 ( 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, interception parties code-named headaches were embarked on warships and from May 1942, computers sailed with the cruiser admirals in command of convoy escorts, to read W/T signals which could not be intercepted by stations in Britain. The Admiralty sent details of wireless frequencies, call signs and the daily local codes to the computers. Combined with their knowledge of procedures, the computers could give fairly accurate details of German reconnaissance sorties and sometimes predicted attacks twenty minutes before they were detected by radar. In February 1942, the German (, Observation Service) of the (MND, Naval Intelligence Service) broke the British Naval Cypher No 3 and was able to read it until January 1943.