An Operation Outward balloon over Böhlen

On 12 July 1942 a small unmanned rubber balloon, released the day before from the Suffolk coast as part of the British Operation Outward, drifted over Saxony and caught the steel wire trailing beneath it on a 110 kV high-voltage line near Leipzig. The short circuit it caused carried through to the power station at Böhlen, a dozen or so kilometres south of the city. According to post-war British findings, the circuit breakers there failed, one of the generators fell out of synchronism and was wrecked, and an explosion and fire destroyed the power station. It was the greatest single loss inflicted on Germany by the Royal Navy’s campaign of cheap balloons. Many accounts speak of “a power station near Leipzig”; more precisely, it was Böhlen, an industrial town south of Leipzig.

Böhlen

In the 1930s Böhlen was one of the centres of central German industry based on brown coal (lignite). A large opencast mine was opened there in 1924, and in the following years a power station was built beside it, supplying electricity and steam to local industry and to the regional grid. Next to the mine stood a plant of the Brabag company, which produced synthetic fuels from lignite for the armed forces. The whole complex lay far beyond the reach of daylight raids, and in 1942 RAF night bombers ventured over Saxony only rarely and to little effect. With a favourable wind, however, a balloon could reach the Leipzig area.

How it happened

About half the balloons of Operation Outward carried, instead of an incendiary load, some hundred metres of thin steel wire suspended from a longer hemp line. As the balloon descended, the wire trailed low over the ground for several dozen kilometres until it snagged on the conductors of a transmission line. British trials in 1940–1941 had shown that a wire drawn across two phase conductors produced an electric arc several metres long, which lasted until the protection tripped. The German grid was well protected against earth faults but much less well against phase-to-phase faults, which could damage not only the lines but also transformers and circuit breakers.

That, according to post-war findings, is what happened on 12 July. A phase-to-phase short circuit on the 110 kV line caused the circuit breakers at the Böhlen power station to operate faultily. One of the 16.5 MW turbo-generators fell out of synchronism with the grid and began to vibrate violently. Its shaft bent, the rotor began to rub against the stator, and then came an explosion, and a fire destroyed the power station. According to the British team that investigated the effects of the operation after the war, some 250 MW of capacity was put out of action for a long time, and the material damage was estimated at about a million pounds at 1942 prices, not counting the value of lost production.

These figures must be read with caution. They are known from British studies, cited among others in an article by Raoul E. Drapeau in the American power engineers’ journal IEEE Power & Energy Magazine in 2011, and not from published German documents. The British report of 1946 itself estimated the total damage caused by the whole operation, on the basis of the available records, at about one and a half million pounds, while noting that the data were incomplete: documents from the Soviet occupation zone, in which Böhlen lay, were missing, and records from 1943–1944 were increasingly unreliable. The damage at Böhlen was thus certainly the operation’s greatest known success, but its exact scale remains an estimate.

Balloons and the defence of the Reich

July 1942 was a period of expansion for Operation Outward. The first balloons had been released from a golf course near Felixstowe on 20 March. In July a second site was opened above Oldstairs Bay near Dover, and in August the rate rose to a thousand balloons a day. Each cost less than two pounds. By comparison, a couple of weeks earlier, in the thousand-bomber raid on Bremen, the RAF had lost 48 aircraft with their crews.

The Germans took the balloons seriously. The Luftwaffe sent fighters against them – according to British figures, as many as 250 aircraft on one occasion – and fired on them with anti-aircraft guns. Power companies switched off lines along the expected flight paths and increased the sensitivity of their protection, and, according to Drapeau’s article, produced more than a million special clamps intended to protect the conductors. The clamps proved harmful, since they themselves disconnected the lines, and were removed. Power cuts on lower-voltage lines became so frequent that after a while they were no longer recorded. The British were particularly pleased by the balloon hunts: shooting each one down cost the Germans more in fuel and aircraft wear than it cost the British to make it.

The balloons, however, did not choose their targets and knew no borders. Some came down prematurely in occupied Belgium, some were blown back over England, and some reached neutral countries, which led to diplomatic protests from Switzerland and Sweden. In Sweden, indeed, damage had already been caused in September 1940 by British barrage balloons that had broken from their moorings – the origin of the whole idea – and the most serious incident occurred on the night of 19–20 January 1944 near Laholm, where two trains collided, according to British accounts after a balloon had damaged the railway power supply.

Place in the war

Böhlen showed what a weapon of chance could achieve: one balloon costing less than two pounds put out of action for a long time a power station that bombers would have had to cross the whole of Germany to destroy. But it was a success of its own kind, never repeated. Operation Outward continued until 4 September 1944; 99,142 balloons were released, and its real effect was the constant harassment of German power supplies and air defences rather than destruction. For Winston Churchill, who in September 1940 had ordered the idea to be investigated, and for the Admiralty, it was proof that even very modest means could force the enemy into costly defence; the outcome of the war, however, was decided by bombers, not balloons.

Böhlen’s industry remained an Allied target. When in 1944 the American and British air forces began their offensive against the German synthetic fuel industry, the Böhlen plants were put on the target list and were bombed many times in 1944–1945. By then they were worked by forced labourers, prisoners of war and inmates of a subcamp of Buchenwald.