Part 7-2. Confound and Destroy IV: Corona, Airborne Cigar and the Collapse of German Nightfighting
Before going any further, it is worth looking at another front in the RCM war: that of the communications battle. The introduction of 'free fighting' Wilde Sau
and Zahme Sau
tactics by the Luftwaffe gave Bomber Command another target for their RCM effort. The new tactics relied in part on a running radio commentary from ground controllers that broadcast a verbal picture of the air battle to the German pilots. Special Tinsel was a help in drowning out the HF-band frequencies with noise (see Part 6) but the Germans were overpowering it with high-powered transmitters and the VHF bands were still clear. One solution to this was 'Corona', a cunning plan in which German-speaking RAF personnel, most of them Jewish refugees with native accents, began broadcasting fake controller instructions to the German pilots.
On the first night Corona was used, 22/23 October 1943, the Luftwaffe controller was reduced to apoplectic rage by the tactic, screaming 'Don't be led astray by the enemy' to his fighters. When he started cursing into his microphone the RAF 'ghost' controller was to tartly respond: 'The Englishman is now swearing!' prompting the German to shout 'It is not the Englishman who is swearing, it is me!'
This was all good knockabout stuff, but it was clear that the fake running commentary was easily detected and countered. So the RAF started to be smarter in their use of Corona, such as using it to broadcast fog warnings at airfields to encourage nightfighters to return to base. In some cases this led skeptical pilots to disregard genuine fog warnings, and get in trouble as a result. Corona would also ask for test transmissions from pilots so as to tie up the frequencies.
The Germans countered by using women to broadcast instructions, believing the RAF would never put women counterparts in their bombers. The Luftwaffe did not realize that signals in the 3-6 MHz HF band bounced off the ionosphere, allowing Corona to broadcast safely from a monitoring station in Kent, so the RAF responded by deploying German-speaking WAAFs as 'ghost' controllers. A possibly apocryphal story claims the Luftwaffe tried to counter the 'ghosts' by using opera singers to sing instructions to the pilots. It's also said, more reliably, that on occasion the German controllers and their RAF tormentors (the women in particular) would abandon all attempts to issue real or fake instructions and engage in bitter personal abuse; a kind of 'flame war' that would gum up the bandwidth. As pilots got wise to Corona a new technique was introduced, broadcasting turgid passages from Goethe and records of Hitler's speeches to clutter the airwaves. PHOTO: German-speaking signals personnel operate the Corona countermeasure. The WAAF transcribes the signals traffic and the gramophone record plays superimposed voices to jam the airwaves.
Bomber Command had another card up its sleeve, in the form of 'Airborne Cigar' (also known as 'ABC') a jammer that would bedevil the German VHF frequencies. Operators in specially modified Lancasters would listen for broadcasts and then tune their ABC transmitters to jam it. They would then respond as the defenders tried to retune their broadcasts, driving the German operators bananas as they chased the transmissions up and down the spectrum.
By late 1943 the airwaves were full of clutter from bell sounds, a continuous 'doodle-doodle-doodle' noise, Hitler speeches and other garbage. Even the Anne-Marie Forces broadcasting station was being jammed, for the reason that the Germans were using it to transmit information to the nightfighters. The station would play waltzes if bombers were in the Munich area and jazz if near Berlin. Church music meant Münster, Rhenish music Köln, and so on. A high-powered British jammer codenamed 'Dartboard' soon put a stop to that game. When the Luftwaffe began broadcasting messages in Morse Code--notoriously hard to jam--a new British transmitter dubbed 'Drumstick' sent meaningless strings of Morse to mask the real messages. The Luftwaffe could only counter this barrage of jamming by broadcasting simultaneously on multiple channels. Frustrated aircrews had their work cut out searching for an unjammed frequency, and there was no guarantee it would remain clear for long.
The Germans had to turn to other forms of communication. Flak could fire patterns of flares to give signals to fighters aloft. Searchlights could semaphore the identity of the target cities. Beleuchtergruppen
, formed of special bomber aircraft, flew special missions above the bomber stream, dropping lines of flares that would draw fighters for hundreds of miles around. ILLUSTRATION: This Lancaster W-William of 101 Squadron is equipped with Airborne Cigar. The huge blade aerial on the chin is for the 50-Watt transmissions, and the twin masts on the top of the fuselage for the 40-Watt transmitters. For the jamming to be effective, ABC had to get close to the source of transmissions, so ABC aircraft would fly within the stream, conducting regular bombing missions. An additional radio operator was added to the crew to run the system.
The was the environment into which 100 Group (Bomber Support) intruded in the summer of 1944, launching spoof missions every night that weather permitted, even when real bombing operations were not planned. Mandrel screens concealed the forces moving behind them, and then the spoof force would emerge from the screen to draw the nightfighters in one direction while the real bomber stream emerged travelling in a different direction. They would be escorted by RAF Flying Fortresses and Liberators equipped with a new jammer, 'Piperack', that could blank out any SN-2 radars pointed at it. 100 Group had yet another toy to play with, 'Jostle IV', which was the biggest jammer yet built. It had been created by Metropolitan-Vickers almost by accident, in response to an casual suggestion by one of the chief British scientists. The government was somewhat upset at being saddled with a half-million pound bill for the thing, but in a business where power is everything, Jostle IV was a beast of a jammer that proved able to drown out communications at a distance in the Luftwaffe's 38-42 MHz VHF band.
Thus armed, 100 Group began to tip the night bombing campaign in favour of the Allies. In truth many factors were coming into play. The invasion of Europe was collapsing the front line of the air defences and fuel shortages were beginning to bite. But the Serrate-equipped Mosquito intruders were beginning to wear down the Luftwaffe's cadre of nightfighter aircrews at the rate of one or two each raid. As fuel shortages meant that only the most experienced men were sent up to defend the Reich, this meant that an irreplaceable resource was being bled away.
In the autumn of 1944 Bomber Command's losses suddenly declined, and the constant harrying by 100 Group meant that they were never to recover. Generalmajor Adolf Galland, the fighter ace now commanding the entire fighter force, was to remark:
"Today the nightfighter achieves nothing. The reason for this lies in the enemy jamming operations, which completely blot out ground and airborne search equipment. All other reasons are secondary." Next:
Night Hunters: Developing the Ultimate Night Fighter.
You can order Nightfighter: Air Warfare in the Night Skies of World War 2