'Bodden' was a German undertaking, supervised by the Abwehr military intelligence department, for the gathering of intelligence in Spain and Morocco (1938/January 1944).
Between 1939 and January 1944, the intelligence services of Germany and Italy, with the assistance of the Spanish government, maintained a network of stations in the vicinity of the Strait of Gibraltar. These stations tracked the movements of Allied warships and merchant vessels, and were thus an invaluable source of intelligence to the Axis for attacks on Allied convoys. The British government considered attacks on the stations on two occasions during 1942 but decided instead to use diplomatic pressure to have them closed. The stations are believed to have ceased operations in January 1944.
The German and Italian intelligence services established a network of ship-watching stations along the coasts to the north and south of the Strait of Gibraltar, in Spain and Spanish Morocco respectively, during the early years of World War II.
While the efficiency of the ship-watching organisation was initially poor, by the autumn of 1941 it had grown into an effective source of intelligence. By this time the Axis forces were operating southern stations at Alboran island, Cape Tres Forcas, Ceuta, Melilla, Tangier and Tetuan, and northern stations at Algeciras, Cape Trafalgar, Cap de Gata, Málaga, and Tarifa. Two of the stations were manned by Spanish personnel and the others by Spanish, German and Italian personnel. The Germans and Italians are believed to have worn Spanish uniform to conceal their presence. The station at Algeciras, lying directly across the Bay of Gibraltar from the British territory, was the most important of the stations, and radioed at least 20 reports each day to the Abwehr's headquarters in Berlin.
The British government was aware of the Axis ship-watching network and monitored its activities by decoding the radio signals sent by Abwehr personnel. While the British had no way of countering the network in 1941, this intelligence enabled the development of limited countermeasures. Allied ships operating near Gibraltar, for example, were instructed to sail during periods of poor visibility and take evasive courses. The British intelligence services were able to advise the naval command at Gibraltar of the ship movements which had been reported by Axis forces.
Late in 1941, construction began on buildings to house German equipment which would allow ships to be tracked using infra-red and other short-wave apparatus at nine sites on the northern coast of the Strait of Gibraltar and five on its southern coast. This was 'Bodden' proper, whose primary technology was the bolometer, which could to detect heat rising from nearby vessels, and the first of these installations began operations in February 1942. Following approval from Vichy Franco in he following month, the network was active by mid-April 1942. As a result of 'Ultra' intelligence gained from the interception and decryption of Abwehr radio traffic, the British were able to monitor the installation of the new equipment and consider responses to it.
Kim Philby of MI.6 kept watch on Abwehr operations and consulted Dr R. V. Jones, the assistant director of intelligence (science) at the Air Ministry. Jones inferred that 'Bodden' was designed to install an 'infra-red burglar alarm' to count ships into and out of the Mediterranean. It appeared that there would be three parallel infra-red searchlight barrages, just to the west of Perejil island, shining north toward Algeciras. The strait there is some 10 miles (16 km) wide and Jones believed that the method could be unreliable because of twinkling just above the sea. A larger infra-red detector with longer range was to be set up near Algeciras pointing south to detect hot spots on ships such as funnels. If the devices became operational, the Royal Navy would have to lag the funnels of their warships or to send decoys back and forth.
On 7 March, the authorities at Gibraltar were warned by the Admiralty that ships operating near the territory could be tracked at night. In May 1942, the Chiefs-of-Staff Committee discussed attacking the sites by gunfire bombardments from submarines or raids by Combined Operations units. It was eventually decided not to attack the sites for fear that it would provoke a Spanish attack on Gibraltar, and the British ambassador to Spain, Sir Samuel Hoare, was briefed on the scientific aspects of the German operation and directed to raise the matter with the Spanish government. Hoare insisted on meeting General Francisco Franco y Bahamonde, the Spanish dictator, to discuss the new ship-watching stations. During their discussion on 27 May, Hoare presented a detailed account of German activities in Spain and indicated that petrol supplied by Allied countries had been used as part of the construction of the facilities. Franco denied that the network existed and claimed that the German personnel were providing technical assistance to Spanish coastal artillery batteries. Franco inferred that Hoare’s comments were a threat to cut off the supply of petrol and promised to conduct a personal inquiry into the matter. Franco met with the head of the Abwehr, Admiral Wilhelm Canaris, in June and directed that the stations be closed.
On 3 June the Spanish admitted that the Germans had installed devices for coast defence but denied that facilities had been provided for 'foreign interests' and offered an assurance that shipping would not be attacked using information from the installations. Canaris’s subsequent attempts to persuade Franco to rescind this decision failed and on 1 July the Spanish foreign minister provided Hoare with an assurance that the sites built during 'Bodden' would be closed and the Germans sent home, yet the Germans claimed that information from the installations was used for an attack on a convoy passing the straits on the night of 11/12 July. While these sites were no longer operational by the middle of July, the Allies learned from 'Ultra' decrypts that the Germans were installing the equipment in new locations on Spanish territory.
During July and August, two new bolometer sites began operations near Algeciras and Ceuta. These detected the 'Pedestal' convoy bound for Malta, during the second week of August 1942 and Axis air, sea and submarine attacks led to many losses. Following this engagement, the Chiefs-of-Staff Committee again considered countermeasures against the bolometer sites: the governor of Gibraltar and the Special Operations Executive proposed direct attacks on the facilities, while Admiral Sir Dudley Pond, the First Sea Lord, advocated jamming them. During a meeting on 25 August, the Chiefs-of-Staff Committee decided that the best course of action was the delivery of another diplomatic protest, which was formally lodged with the Spanish government in October.
This protest did not lead to the closure of the stations and it is likely that they played a role in the Axis response to the Allied 'Torch' landings in North Africa in November 1942. The sites were not the only source of intelligence used to direct air attacks on Allied convoys, as the Luftwaffe undertook a daily reconnaissance flight over Gibraltar from September. The bolometer sites were dismantled late in 1942, and on 29 December, after the Spanish government directed Canaris to cease intelligence activities in Spain and therefore prevent giving the Allies a pretext to invade the country. German observation posts continued to be maintained in the Gibraltar area, though the German agents were gradually replaced with citizens of other countries and the sites declined in effectiveness. An attempt to reactivate the bolometer sites was made in the middle of 1943 but abandoned by July.
Later in 1943, the Spanish government, still under pressure from the Allies, ordered the closure of the remaining ship-watching stations, and there is no evidence that any stations operated after January 1944. Sir Harry Hinsley judged in the official history of British Intelligence in the Second World War that the ship-watching operation had been 'the most important' form of assistance Spain provided to the Axis during the war.
In 1943, Jones found that a German Elektra Sonne station was being set up near Lugo in north-western Spain as part of a navigation system for aircraft and U-boats. Jones used photographs of the station to establish how it worked and supplied RAF Coastal Command with instructions to use it under the codename 'Consol' as it was of more use to the British than the Germans and simpler than 'Gee'.