'Wilde Sau' (i) was the German use of unguided attacks by night fighters against British night bombers over North-Western Europe, and especially Germany (June 1942/January 1944).

The tactic was introduced after the Allied air forces had gained a major advantage over the German radar-controlled interception system, and involved the fighters engaging the British bombers freely as the latter were illuminated by searchlight batteries while also avoiding their own anti-aircraft fire. After some initial successes, rising losses and deteriorating weather conditions led to the abandonment of the tactic.

The background to the tactic’s development and introduction was the fact that in the course of 1943 the weight and frequency of Allied bombing raids against German industries and cities had intensified significantly. Over-pressed by the need to fight on several fronts, the Luftwaffe could find no adequate answer to these raids. Previous mismanagement by the Luftwaffe leadership had led to a stagnation in the production of much needed aircraft, and indecision about air doctrines exacerbated the situation.

Another blow was the British seizure of a Junkers Ju 88R-1 night fighter when its crew defected and flew to Scotland. This aeroplane was equipped with the initial B/C form of the 'Lichtenstein' air-interception radar, whose existence and details were thus revealed to the Allies. Air Chief Marshal Sir Arthur Harris’s RAF Bomber Command then began to use a new form of 'Window', the aluminium-strip chaff sized to jam the 'Lichtenstein B/C' radar. This demanded that the Germans develop and deploy a new night-fighting tactic not reliant on air-interception radar until the longer-wavelength 'Lichtenstein SN-2' radar could be produced for use in German night fighters. By mid-1943 it became clear that the past approach was not working and a change in the general aerial defensive doctrine was needed. One of those was the introduction of new fighter tactics to counter the increasing threat of British night bombers.

On 27 June 1943, Major Hajo Hermann of the Luftwaffe proposed an experimental approach he had already evaluated in secret trials. This concept was expanded by Oberst Viktor von Lossberg, who on 29 July presented the proposal to the Luftwaffe leadership, more specifically Generalfeldmarschall Erhard Milch and Reichsmarschall Hermann Göring. Successful trials of the new tactic convinced them, and also Adolf Hitler, to order the use of the tactic.

The new tactic was based on the use of free-ranging day fighters and, to a lesser extent, night fighters. The single-engined fighters were to supplement the ground-controlled 'Himmelbett' technique, by co-operation with searchlight crews over the target area. Pyrotechnic and other visual means were used to guide the fighters in the resulting 'Wilde Sau' (i) system. After the fighters had reached the combat zone, pilots tried to identify and intercept British bombers visually with the aid of searchlights used to illuminate the sky. Initial tests using former flying instructors, who were experienced in blind-flying techniques, suggested the ideal weather condition for the successful employment of the new tactic was lower-level cloud of medium density: in such conditions, the bombers were silhouetted against the back-lit clouds and the high-flying German fighters could spot possible targets without difficulty.

During trials, ceasefires with the German Flak units were arranged to prevent 'friendly fire' incidents, but it became apparent that the co-ordination of ceasefires with 'Wilde Sau' (i) operations was difficult. To remove this threat from their own Flak, the fighters were ordered to fly at particular altitudes so the Flak could avoid engaging them. Another problem was navigation. As night-flying aids in any day fighter were rudimentary, there was the need for an elaborate system of visual aids to navigation, these aids including light beacons, searchlight patterns, Flak firing combinations of various tracer colours through the clouds, and parachute flares. The provision of such aids was a lengthy process, so as a short-term expedient converted bomber pilots were used as these already had experience with nocturnal navigation. Another navigation aid was simply the target of the Allied bombing: a city illuminated as it burned would guide the fighters to their target.

The week-long 'Gomorrah', otherwise the Battle of Hamburg, in July 1943 was a disaster for the Luftwaffe as the first use of 'Window' by RAF Bomber Command’s aircraft effectively disrupted the 'Himmelbett' radar defence system: 'Window' blinded the ground-controlled intercept system, airborne radar sets, gun-laying radar and searchlight controls, and as a result the British losses to Flak and night fighters declined radically. The campaign was aided by the prevailing weather conditions, which led to the emergence in Hamburg of a firestorm. As they considered how to offset this major British advantage, the Germans considered every measure with offered the possibility of preventing any recurrence, and Hermann’s proposal was put into effect. His original experimental unit was rapidly expanded into the Jagdgeschwader 300, which was soon supplemented by the JG 301 and JG 302 were also to create the new 30^th Jagddivision, commanded by Hermann, who was promoted to the rank of Oberst.

On the night of 3/4 July, 653 RAF Bomber Command aircraft attacked Köln and the 'Wilde Sau' (i) squadrons took part in the city’s defence. The Luftwaffe shot down 30 British aircraft, of which 12 fell victim to 'Wilde Sau' (i) fighters, which operated above the designated ceiling of the Flak batteries. After this success and Lossberg’s subsequent influential report, the use of the 'Wilde Sau' (i) tactic was increased and together with the complementary 'Zahme Sau' tactic was integrated in a new German air defence system. This was all part of a larger reformation of the German air defence arrangements and the armament industry in the summer of 1943. These measures accelerated the abandonment the 'Himmelbett' system and paved the way for a more flexible tactical approach to the problem posed by British night bombers. The reforms were initially successful as indicated by the increase in fighter victories and industrial production.

During the air battles of the summer and autumn of 1943, the Germans were able to deal some significant blows to the British night bomber forces with the aid of the new tactic. During the deception bombing raids on Berlin and 'Hydra' (ii) raid on the Peenemünde research facilities during the night of 17/18 August, 64 bombers were shot down. In another raid on the night of 23/24 August, 56 bombers were shot down, representing 8% of the attacking force. These air battles also saw the first operational implementation of schräge Musik, which was a pair of cannon, usually of 20- or 30-mm calibre, in an oblique dorsal installation in the fuselage to allow night fighter pilots to close on and engage their targets from the latter’s most vulnerable ventral angles.

The success continued and the new tactics were improved as night fighters were able to inflict heavy losses on the British during the next period of the bombing campaign in the autumn and winter of 1943. In December alone the British lost 316 bombers.

Even so, the success of the 'Wilde Sau' (i) concept was short-lived, and also proved very costly for the 100 or so fighters of the 30^th Jagddivision. The tactic was thus only a stopgap measure, and while larger numbers of British bombers were shot down, German losses also rose significantly. The Luftwaffe was not able to replace its losses, especially of skilled pilots, and as a result of the high attrition rate fighter readiness declined. The use of the same aircraft for both the day fighter and nocturnal 'Wilde Sau' (i) night-fighter operations amplified this effect and the resulting erratic scheduling of maintenance led inevitably to a drastic drop in serviceability rates. With the onset of poorer weather in the autumn of 1943, wastage through accidents and icing soared, and pilots could not use the 'Wilde Sau' (i) tactic as effective as they had in better weather. The use of the 'Wilde Sau' (i) tactic ended in the spring 1944, but had nonetheless allowed the Luftwaffe to maintain an air defence capability pending the advent of new radar equipment immune to 'Window'.