The Sturmböcke

The introduction of heavy bombers from the United States Army Air Forces created a dilemma for the German fighter force. The B-17 Flying Fortress was exceptionally tough, and the armament of the Bf 109 and Fw 190 was insufficient for bomber-destroyer missions.

The eventual employment of the B-17 in combat box formations gave lethal massed firepower from a hundred or more Browning AN/M2.50 calibre machine guns.

Furthermore, while successful against unescorted Allied bomber formations, the Luftwaffe's original solution of Zerstörer twin-engine Messerschmitt Bf 110G bomber destroyers lacked mobility and were annihilated by the USAAF's fighter escorts in late 1943 and early 1944.

Two original Wilde Sau single-engined night fighter wings, Jagdgeschwader 300 (JG 300—300th Fighter Wing) and JG 301, were rebuilt for their usage. These units were made up of Sturmböcke. JG 3 did, however, have a specific gruppe (group) of Sturmböcke.

The Fw 190 was built as a tough interceptor capable of withstanding significant combat damage and delivering a forceful 'punch' from its steady gun carriage, making it excellent for anti-bomber operations.

To accommodate bigger armament, Focke-Wulf altered elements of the wing construction. The Fw 190 A-6 was the first sub-variant to receive this modification. Its conventional weaponry was reduced from four MG 151/20s to two, with four additional cannons in two underwing cannon pods.

The plane was known as the A-6/R1 (Rüstsatz; or field conversion).

The first plane was delivered on November 20, 1943. During brief trials, the dual cannons were replaced by an MK 108 30mm autocannon in the outer wing, which became the A-6/R2. The cannons were powered by blowback, featured electric ignition, and were belt fed. The 30mm MK 108 was simple to build and inexpensive; the majority of its components were just pressed sheet metal stampings.

The GM-1 (nitrous oxide) Boost was introduced to the BMW 801 engine in the A-6/R4 to improve performance at high altitude. The canopy now has 30 millimetres (1.2 in) of armoured glass for protection. The A-6/R6 was outfitted with twin heavy calibre Werfer-Granate 21 (BR 21) unguided air-to-air rocket launchers (one per wing).

The enhanced improvements, particularly the powerful firepower, transformed the Fw 190 into a formidable bomber-killer. The A-7 was born in November 1943. The twin cowl-mounted synchronised 7.92mm (.318 cal) MG 17 machine guns were replaced by two synchronised 13mm (.51 calibre) MG 131 machine guns. Two 30mm MK 108s and two BR 21 rockets may be carried by the A-7/R versions. This boosted its effectiveness as a Pulk-Zerstörer (Bomber Formation Destroyer). The A-8/R2 was the most common Sturmbock aircraft, with 900 constructed by Fiesler in Kassel and outfitted with 30mm MK 108s in its outer wing panel mounts.

While still capable bomber-killers, the Fw 190's armour and considerable up-gunning with higher calibre ammunition made it difficult to manoeuvre. They had to be escorted by Bf 109s because they were vulnerable to Allied fighters. However, when the Sturmgruppe was able to function properly, the results were devastating. With heavily protected engines and cockpits, the Fw 190 As were attacked from behind, and gun camera footage shows that these attacks were frequently pressed to within 100 yards (90 m).

US Response

During the American daylight section of the Combined Bomber Offensive, US fighters who maintained close touch with the bombers they were escorting were unable to pursue any assaulting Luftwaffe fighters, forcing them to turn back and return to the bombers. As a result of the significant losses, the Allies devised a strategy.

Major General Jimmy Doolittle gained command of the Eighth Air Force in January 1944 and made a key modification to bomber escort doctrine by "freeing the fighters". Previously, American fighter pilots on bomber escort missions were required to stay with the bombers at all times.

Instead, on the outer legs, they would fly far ahead of the bomber formations in air superiority or "fighter sweep" mode, then roam far from the bomber streams "cleaning the skies" of any Luftwaffe fighter opposition towards the target.

Though Doolittle's strategy change was unpopular with the bomber crews, its repercussions were quick and powerful. Initially, P-38s and P-47s filled this job, but by the spring of 1944, both kinds were gradually supplanted by the longer-ranged P-51s.

In reaction to American air superiority tactics, the Luftwaffe formed the Gefechtsverband (battle formation). It was made up of a Sturmgruppe of heavily armed and armoured Fw 190s escorted by two Begleitgruppen of light fighters, mostly Bf 109s, whose job it was to keep the Mustangs away from the Sturmböcke Fw 190s assaulting the bombers. 
The massive German formation took a long time to assemble and was difficult to manoeuvre, making this design ideal in theory but impossible to implement in practise.

It was frequently intercepted by accompanying P-51s using modern "fighter sweep" tactics out advance of heavy bomber formations, breaking up the Gefechtsverband formations before they reached the bombers.

While they were not always able to avoid contact with the escorts, the possibility of mass attacks and, subsequently, "company front" (eight abreast) assaults by armoured Sturmgruppe Fw 190s created a sense of urgency to fight the Luftwaffe wherever it could be found, whether in the air or on the ground.

Beginning in late February 1944, 8th Air Force fighter units launched systematic strafing raids against German airfields that grew in regularity and severity during the spring, with the goal of obtaining air superiority over the Normandy campaign. In general, they were carried out by units returning from escort flights, but starting in March, several groups were also given airfield attacks rather than bomber support.

The P-51, especially with the introduction of the K-14 Gyro gunsight and the development of so called "Clobber Colleges" – created for the training of fighter pilots in 1944, was a decisive element in Allied countermeasures against the Jagdverbände.

The price of failure

This plan terminally damaged the Zerstörergeschwader heavy fighter wings, which consisted of Zerstörer twin-engined Bf 110Gs followed by Sturmbock Fw 190 A replacements, wiping each group of bomber destroyers from Germany's skies in turn for the most of 1944.

The USAAF's aircraft were free to strafe German airfields and cargo as part of the new tactic, especially while returning to base after the bombers had struck their targets. These extra raids were critical in Allied air forces achieving air superiority over Europe.

Further reading