World War II: Suppression of Enemy Air Defence (SEAD) II

One of the methods of doing this was to use specially-equipped aircraft, known as Ferrets. These aircraft, were modified B-17F Flying Fortresses which carried no bombs, but were instead fitted with an APA-24 Direction Finding antenna which would listen and record the radio frequencies that German radar used. This enabled the Carpet system, and later the Mandrell radar jamming equipment, then to be tuned to that wavelength to produce interference to disrupt the radar and thus make the flak inaccurate. The equipment would be mounted in the lead aircraft of a bomber formation and was credited with some considerable success in spoofing the Luftwaffe’s radar. The USAAF had the 16th Reconnaissance Squadron based at Foch airfield, Tunisia, and used Boeing B-17F Ferrets on bombing raids into Europe.

B-17F Ferret missions began in 1943 and had several objectives in mind. The first was to monitor the radar stations and locate their position which could then be attacked by other bombers. The immediate effect would be to cost the Germans precision in their flak direction, thus rendering it less effective. However, the destruction of the radar would have other effects. Radar was a time-consuming and intricate thing to build. Line replacement units could not be mass produced like artillery shells and, therefore, it would take time to replace equipment that had been destroyed and would lead to a subsequent gap in coverage which the Allies could then exploit. Secondly, once they realised that they were the target, the morale of the German radar operators was bound to suffer, as was the morale of the personnel manning the flak emplacements as they realised that their fire would be increasingly inaccurate. Finally, the strikes on the radar stations would kill experienced German radar operators, thus depriving the Luftwaffe of the training cadre who could pass their wisdom onto younger generations who would need to learn the mysteries of radar afresh. Moreover, radar and personnel which survived the attacks would become increasingly overloaded as other units were lost and therefore less effective. Thus, the German air search radar was the CoG in their flak system.

The first Ferret missions by the 16th Reconnaissance Squadron were performed on 21 April 1943 from Tunisia and the unit continued to perform its missions notably supporting Operation Avalanche, the Allied invasion of Italy, when it supported landing operations on the island of Salerno in September 1943. As the year drew to a close, the squadron would have a total of thirty-five B-17F Ferret aircraft at its disposal. The unit came to the fore during the Big Week bombing campaign of 20-25 February 1944 which unleashed a massive campaign against the German aviation industry and helped the Allies to achieve air superiority prior to Operation Overlord in 1944.

The USAAF was not alone in developing specially equipped aircraft for radar hunting. The RAF was working on Project Abdullah by 1944. Abdullah was the codename for an electronic radar hunting device that was fitted to three Hawker Typhoon aircraft which belonged to 1320 Special Duty Flight in May 1944. Abdullah consisted of a Cathode Ray Tube (CRT) which was connected to a radar homing receiver. This receiver could be tuned to the known operating frequencies of German radar. The equipment would be switched on and the Typhoon would fly around the area where radar was suspected and wait for the Abdullah equipment to pick up the radar transmissions. Once Abdullah alerted the pilot that radar was active, the pilot would visually try to acquire the target. They would then fly towards it and fire smoke rockets to mark the target for their accompanying escort of ground-attack aircraft. These tactics were not unlike those which would be used by the earliest Wild Weasel aircraft in the Vietnam War.

The initiative was an impressive step forward but, as with Sir Issac Newton’s dictum that every reaction has an equal and opposite reaction, the presence of the Abdullah aircraft would lead the German radar operators to switch off their radar once they had learned that keeping it switched on invited attack. The Germans pioneered this technique which would be used time and again by radar operators in every conflict henceforth. Keeping radar activated invites attack, switching it off invites safety. However, Abdullah had other shortcomings. The radar receiving equipment had to be preset to a particular German radar frequency before the aircraft took off for its mission. If the Germans changed their radar frequency, then the Abdullah aircraft would have no way of locating the radar.

One of the most notable SEAD raids occurred during Operation Market Garden in September 1944, made famous by Cornelius Ryan’s book A Bridge Too Far, which relates the brave Allied attempts to seize the bridges over the Waal and Rhine rivers at Njimegen and Arnhem respectively to open the next stage of a land route into Germany following the liberation of Belgium and France. The operation was to feature a significant effort by the Eighth Air Force to perform SEAD against German flak emplacements posing a grave threat to the airborne landings of the First Allied Airborne Army and their accompanying 1,438 C-47 Dakotas, and over 3,000 gliders which were to dispense the American, British and Polish airborne forces to take bridges at Son, Veghel, Grave, Njimegan, Arnhem and Oosterbrook across a north-east/south-west axis. The airborne operation to seize the bridge was absolutely imperative to the overall success of Market Garden as they awaited the arrival and reinforcements of the British XXX Corps. The flak emplacements were a clear and present danger.

The Eighth Air Force’s orders were to bombard ‘the antiaircraft installations along the routes to be followed by the troop carrier aircraft and in the areas surrounding the drop and landing zones. The B-17s belonging to the 1st and 3rd Bombardment Divisions based in the UK, were earmarked for the task. Photographic reconnaissance had provided those planning the operation with up to 112 targets for the B-17s. Needless to say, this was to be a classic example of the mass approach to SEAD. The aircraft were to carry fragmentation bombs as they would be attacking from altitude and thus area attacks to hit the flak emplacements would be more appropriate. Low-level attacks were the preserve of the faster, more agile fighter-bombers.

Prior to the airborne operation on 17 September, an armada of 872 bombers heaved themselves into the late summer air and made their way to towards their targets in the Netherlands. Over the bombardment area, these aircraft dispensed their ordnance onto the AAA emplacements below, but that did not stop them suffering damage from their indented victims.

The Flying Fortresses were not alone; they were joined by P-47 Thunderbolts from the Eighth Air Force. Their task was to get in close and hit flak emplacements which covered the southern ingress routes for the Dakotas. These aircraft were joined by a further four groups of P-47s from the Ninth Air Force. The P-47 was the ideal tool for the task. With its rugged, sturdy construction the aircraft could take a fair degree of punishment which was very important given the strength of German anti-aircraft artillery in the area of operations. But these aircraft gave as good as they got. They were outfitted with eight 0.5-in (12.7-mm) M2 Browning machine guns and they could also dispense up to 2,000 lb (907 kg) of bombs on the emplacements. During the Market Garden anti-flak operations they dispensed a total of 287 × 260 lb (118 kg) bombs and fired over 122,600 rounds. The tally for the Thunderbolt pilots was eighty flak positions damaged and fifty-nine destroyed.

Market Garden was not the success that was hoped for and still remains a subject of controversy. There is not the space here to discuss the merits and shortcomings of this operation, which can be left to other historians, but there is room to look at the SEAD lessons learned from the operation. The USAAF 56th Fighter Group, which flew Thunderbolts in the operation, noted that thirty-nine of its aircraft began a mission to attack flak targets in the vicinity of Turnhout, south of the Belgian-Dutch border. Weather over the target area, which included fairly low cloud cover and a haze which frustrated the pilot’s visibility scotched hopes of locating the AAA targets from higher altitudes. Moreover, the flak bombardment being suffered by the unit dispersed the formation and claimed the scalps over sixteen aircraft as they were forced down into the weeds both to locate their targets and to press home their attacks. The lesson was obvious, but it was also instructive. The closer the attacking aircraft got to the flak, the more intense the fire became and the likelihood that the aircraft would be shot down increased. Yet, for the bombers the higher altitude the aircraft flew, the less accurate was their bombardment against the flak emplacements unless area weapons were used and these aircraft also had to contend with significant anti-aircraft fire.

The results of AAA suppression during Operation Market Garden were 118 anti-aircraft gun emplacements destroyed and around 127 damaged. However, the cost of this was 104 aircraft lost to flak over 4,320 sorties. AAA suppression sorties, of which the Allies performed 646, cost thirty-seven aircraft. The conclusion from Market Garden was that the use of low-flying attack aircraft for AAA suppression was largely curtailed in favour of passive measures such as chaff and evasive manoeuvres. Another approach was to use artillery to suppress the flak positions before aircraft approached a target. Such measures had already been put into operation during the encirclement of Cherbourg, France, following the Operation Overlord invasion of June 1944. However, the results of the artillery-AAA suppression were mixed. That said, artillery would be used for defence suppression in other conflicts over the next sixty years, notably in the Middle East and later during Operation Desert Storm in 1992.

This joint approach was taken to the issue of flak suppression in March 1945, as the Allies began their Operation Varsity offensive to cross the Rhine at Wesel. The area was surrounded by 922 AAA gun barrels and the Allies suppression efforts saw 8,100 tons of bombs dropped on German AAA emplacements during 3,741 sorties spread over three days. Of these German AAA positions, ninety-five were attacked with 24,000 rounds of artillery though only a few hits were scored using this method. The German flak was not completely suppressed and still claimed 381 American and 160 British gliders of the airborne assault out of a total of 1,125 gliders: over 50 per cent. In addition, AAA also claimed sixteen transport aircraft and fifty-two towing planes. Despite the all-out joint offensive against the German air defences, flak had managed to exact a heavy toll on the Allies. Before the advent of the high-speed Anti-Radiation Missile, SEAD would be a mass affair which would consume large numbers of aircraft and artillery for often limited results.

Major strides were made in defeating AAA along with locating air defence radar as the curtains drew on the Second World War. However, the end of the conflict also betrayed another danger which was waiting in the wings. As the horrors visited on continental Europe by Nazi Germany were being uncovered, so were the technological advances that the Germans had made in the fields of rocketry. Londoners knew to their cost the destruction that these advancements would bring having suffered attacks from the V-1 Flying Bomb proto-cruise missiles, and later V-2 ballistic missiles. However Dr. Werner Von Braun, who led the Nazi rocket research programme, together with his scientists and an army of press-ganged slave labourers had made other key advances in the world of missiles. These included anti-shipping missiles such as the ‘Fritz-X’ but most ominously for pilots, guided anti-aircraft rockets. History tells us that German scientists had perfected the Wasserfall SAM but that Adolf Hitler’s arrogance had scoffed at the project claiming an interest only in offensive weapons, causing it to be neglected until 1943.

It was in this year that the project was revived in the face of increasing Allied bombardment against Germany and the slow death of Luftwaffe air superiority. So it was that on 8 January 1944 that the Wasserfall took to the skies for a test flight. The missile was huge, standing over 25 ft (7.6 m) in height and weighing a staggering 7 tons, yet its speed was in the region of 1,600 ft (500 m) per second and it had a range of 12 miles (20 km). The weapon’s guidance system had been based on the Rheintochter SAM which had been ordered by the German Army in November 1942. The test firings of the weapon, named after the mythical maidens of the Rhine from Wagner’s Der Ring des Nibelungen opera, had begun in August 1943, making the weapon the world’s first SAM and eighty-two test firings were completed and an air-to-air version was also developed, but the weapon would never equip the Army and the project was cancelled on 6 February 1945.

Wasserfall had a radar-based guidance systems. Once in the thick of a formation of aircraft it would detonate. The logic of the weapon was not unlike the later nuclear-tipped anti-aircraft missiles such as the American MIM-14 Nike Hercules which appeared during the Cold War and was designed to use a shotgun approach by detonating a huge quantity of, in this case nuclear, explosive in the middle of a formation to destroy as many enemy bombers or incoming missile warheads as possible. Certainly, Wasserfall was far ahead of its time, but none were ever fired against Allied aircraft. Yet the importance of Wasserfall was that it demonstrated that the Surface-to-Air Missile was a viable concept. This was not lost on the United States and Soviet Union which would use captured German technical documents and German scientists to kick start the development of Cold War missile technology.

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