The Bombing War: Europe 1939-1945

Some of the solutions suggested by scientists brought in to advise the air force and the government were equally far-fetched. One idea was to lay a minefield in the sky in the path of oncoming bombers, on the same principle as a minefield at sea. The object was to attach a small one-pound explosive with a self-detonating mechanism to a long length of piano wire, with a parachute at one end. A line of mines would be laid from an aircraft at right angles to the approaching enemy and as the mines sank at a carefully calibrated speed they were supposed to land on the aircraft wings and explode. Dowding reluctantly agreed to tests in the summer of 1940 but unsurprisingly they proved disappointing.¹⁵⁴ At some point in October 1940 Churchill’s personal scientific adviser, Frederick Lindemann, was converted to the idea of the long aerial mine and persuaded the prime minister to endorse it. Orders were placed for 1 million mines and 24 mine-laying aircraft, but the scheme was always overambitious, since it relied on very precise knowledge of where enemy aircraft would be flying and on perfect timing. It was discovered that the first 1,000 mines delivered all had defective self-detonating devices. When efforts were made in June 1941 to lay the first minefields, only three attempts were made, without any observable success. The scheme was quietly scrapped.¹⁵⁵ Lindemann was also the source of a second fanciful countermeasure. In November 1939 he suggested exploring the use of colloidal coal (a finely ground and treated coal dust) to cover rivers, canals and ports with a non-reflective film to frustrate their use as navigation markers on moonlit nights. Experiments continued throughout the bombing campaign but it was found that winds and tidal waters drove the dust to the edge of the water, making the estuaries or canals more rather than less visible. After two years of experiment a public exercise was conducted in February 1942 on the Thames between Westminster and Vauxhall bridges. Tons of dust was sprayed from converted barges; it gradually gathered at the river’s edge and after two hours sank.¹⁵⁶

It was generally recognized that the only effective way to be sure of destroying an enemy bomber was night-time interception by a dedicated night-fighter aircraft, but it proved beyond the capability of the RAF to achieve this for almost the whole of the German bombing campaign. The problem was regarded as so critical that on 14 September 1940 a committee was set up under the retired Air Chief Marshal Sir John Salmond to investigate the whole issue of night-fighter policy. Three days later the committee presented its findings, recommending a special night-fighter staff, a night-fighting training unit, the decentralization of control over night-fighters to increase speed of response and flexibility, and the introduction of effective radar aids. Great expectations were had of the transfer of a number of single-engine fighter squadrons to night work on clear moonlit nights.¹⁵⁷ Dowding opposed almost all of the recommendations and paid for his resistance with his command. On 1 October he attended a meeting of the Salmon committee where he explained that reorganizing his force would achieve nothing without effective airborne radar (AI = Airborne Interception), which was the only prospect for success. A week later he met Churchill and reiterated his view that the recommended changes would achieve little.¹⁵⁸ He was made to accept the proposed changes with reluctance and on 9 October ordered the activation of nine night-fighter squadrons, six of them in 11 Group in south-east England, including a number of converted Hurricane fighters. On 4 November he was told to introduce more Hurricanes to try to stem the new flow of bombing towards the Midlands, but he told the Air Ministry that without radar detection these efforts constituted nothing more than ‘wishful flying’.¹⁵⁹