'Double Strike' was the very costly US heavy bomber attack on the German war-making industries in Schweinfurt and Regensburg (17 August 1943).

The mission was an extremely ambitious attempt to cripple the German aircraft industry and thereby exercise a strategic effect on the course of World War II in the European theatre. It was known as the 'Double Strike' mission as it was based on two large forces of bombers attacking separate targets in order to dilute the Luftwaffe’s fighter response in time and space, and thus reduce the concentration of Germany’s fighter reaction to the two attacks. 'Double Strike' was also the first US 'shuttle' mission in which all or part of the bombers committed landed at airfields from which they had not taken off, and later bombed another target as they returned to their bases.

After being postponed several times as a result of unfavourable weather, the operation, known within Major General Ira C. Eaker’s UK-based 8^th Army Air Force as Mission No. 84, was flown on the anniversary of the 8^th AAF’s first daylight raid.

Mission No. 84 was an attack by a force of some 376 bombers of 16 bombardment groups against German heavy industry well beyond the range of escorting fighters. The mission inflicted heavy damage on the Regensburg target, but only at catastrophic loss to the force inasmuch as 60 bombers were lost and many more damaged beyond economical repair. As a result, the 8^th AAF was incapable of immediately following 'Double Strike' with a second attack that might have seriously crippled German industry. When Schweinfurt was attacked again, two months later, the lack of long-range fighter escort had still not been addressed and losses were even higher. As a consequence, the US deep-penetration strategic bombing effort was curtailed for five months.

As a result of diversions of bombardment groups to the 'Torch' invasion of French North-West Africa in November 1942, the US bomber force in England had been reduced to four groups of Boeing B-17 Flying Fortress and two groups of Consolidated B-24 Liberator four-engined heavy bombers until May 1943. At that time, and in conjunction with the 'Pointblank' directive, resulting from the 'Symbol' conference in Casablanca, to destroy the Luftwaffe in preparation for the planned 'Overlord' invasion of France, the B-17 force had quickly been expanded fourfold and was organised into the 1^st and 4^th Bombardment Wings, which as a result of their large size would soon be redesignated as bombardment divisions. The 1^st Bombardment Wing, which included all of the original B-17 groups, was based on airfields in the English Midlands while the 4^th Bombardment Wing was based on airfields in East Anglia.

'Pointblank' operations in April and July 1943 had been concentrated on striking at the production of the Focke-Wulf Fw 190 single-engined fighter at factories in Bremen, Kassel and Oschersleben, and although the bomber forces had suffered major losses, the attacks had been successful enough to warrant attacking the factories manufacturing the Messerschmitt Bf 109 single-engined fighter.

Production of the Bf 109 (and almost half of all German fighters) was located in Regensburg and in Wiener Neustadt, the latter in Austria. To attack these in sufficient force, 'Juggler' was conceived, in which the fighter production plants in Wiener Neustadt were targeted for attack by B-24 bombers of Major General Lewis H. Brereton’s US 9^th AAF based on airfields in Libya, and Regensburg by B-17 bombers of the 8^th AAF. The original mission date of 7 August could not be met because of bad weather, and the B-24 bombers flew 'Juggler' on 13 August without the participation of the 8^th AAF, which was still hampered by unacceptable weather conditions.

To complete its portion of the attack, the 8^th AAF decided to attack a target in central Germany as well as Regensburg as a means of tactically dividing and confusing the German air defences. Colonel Curtis E. LeMay’s 4^th Bombardment Wing, using B-17 aircraft fitted with 'Tokyo tanks' for longer range, were to attack the Messerschmitt plants in Regensburg and then fly on to bases in Bône, Berteaux and Telergma in French Algeria. Brigadier General Robert B. Williams’s 1^st Bombardment Wing, following the 4^th Bombardment Wing, was to turn to the north-east and bomb the ball-bearing factories in Schweinfurt, where almost the entire German production of such bearings was centralised, and thus catch German fighter aircraft on the ground re-arming and refuelling. Because of their limited range, as inexplicably they were not employing drop tanks,the escorting Republic P-47 Thunderbolt single-engined fighters would be able to protect the bombers only as far as Eupen in Belgium, which was about one hour’s flying time from each of the targets.

Two supporting attacks were also made a part of the overall mission plan. The first, a diversionary attack, involved the bombing of three locations along the French and Dutch coast: the German airfields at Bryas-Sud and Marck by US Martin B-26 Marauder and British North American Mitchell twin-engined medium bombers, and the marshalling yards at Dunkirk by other Mitchell aircraft, all timed to coincide with the attack on Regensburg.

The second was a series of attacks on Luftwaffe fighter fields at Poix, Lille-Vendeville, and Woensdrecht by Hawker Typhoon single-engined fighter-bombers of the RAF simultaneously with the diversionary attack, and Poix by two groups of B-26 bombers in the afternoon as the Schweinfurt force was returning.

At this time, 8^th AAF bomber operations were calculated on the basis of an allocation of one to two hours for climb and assembly into formations factored into mission lengths. In addition the mission endurance for the Regensburg force was estimated at 11 hours, which meant that commanders had only a 90-minute window in which to launch the mission and still allow the B-17 bombers of the 4^th Bombardment Wing to reach North Africa in daylight. Mission No. 84 planning indicated a take-off window from dawn, at about 06.30 to 08.00 without cancelling the mission.

At dawn of 17 August, after the crews had boarded their aircraft, England was covered in fog. The mission take-off was therefore delayed to 08.00, when the fog had cleared sufficiently over East Anglia to allow the aircraft of the 4^th Bombardment Wing to take-off on instruments, a technique they had practised. Although attacking both targets simultaneously was deemed critical to success of the mission without incurring prohibitive losses, the Regensburg force was ordered to take-off even though the 1^st Bombardment Wing remained grounded at its bases by the adverse weather. By the time the fog had cleared sufficiently over the Midlands, the Regensburg force had already reached the coast of the Netherlands, which indicated that reacting German fighters would have sufficient time to land and replenish before taking off once more to attack the second task force. Consequently, the launch of the Schweinfurt force was further delayed to provide the US escort fighters with sufficient time to return to base to refuel and rearm for a second escort mission. In all, the 1^st Bombardment Wing was delayed by more than three hours behind the 4^th Bombardment Wing.

The Regensburg task force was led by Le May, the 4^th Bombardment Wing’s commander, and the mission would make LeMay’s name as a combat leader. The task force comprised seven B-17 bombardment groups totalling 146 aircraft, all but one of the groups each flying a 21-aircraft combat box tactical formation. The groups were organized into three larger formations termed provisional combat wings, three groups in a V formation wing box leading the procession, followed in trail by two wing boxes of two groups each in echelon formation with one group leading and the second trailing at lower altitude.

About 15 minutes after it crossed the Dutch coast at 10.00, the Regensburg force encountered the first German fighter interception, which continued with growing intensity nearly all the way to the target area. Several factors militated against the Regensburg force in this air battle. The arrangement of two groups instead of three in the two following provisional wings meant one-third fewer guns available to each for their mutual defence and made them more likely targets. The overall length of the task force was too great for effective fighter support. The last wing formation of bombers was 15 miles (24 km) behind the first and nearly out of visual range. Of the two groups of P-47 fighters (87 aircraft) tasked to escort the force to the German border, only one arrived at the rendezvous point on time, and could cover merely the leading wing, and the second arrived 15 minutes late. Finally, both P-47 groups were forced to turn back to base after only 15 minutes of escort duty and without engaging any German interceptors. The last provisional wing in the task force was left without any fighter protection at all.

After 90 minutes of combat the German fighter force broke off the engagement as its aircraft were now short of fuel and ammunition. By then at least 15 bombers had been shot down or fatally damaged, 13 of these from the trailing formation. Flak fire was light over Regensburg and visibility clear, however, and of the remaining 131 bombers, 126 dropped 298.75 tons of bombs on the fighter manufacturing factories with a high degree of accuracy at 11.43.

The Regensburg force then turned to the south to fly over the Alps, confronted by only a few twin-engined fighters, which were in any event soon forced to disengage by lack of range. The German force had not been prepared for this contingency, but they were also in the process of rearming to meet the Schweinfurt force, then forming over East Anglia. Even so, two damaged B-17 bombers turned away from the Regensburg task force and landed in neutral Switzerland, where their crews were interned and the bombers seized. LeMay ordered the formation to perform two 10-minute turns over Switzerland, allowing damaged aircraft to rejoin the formation before flying to North Africa. Another aeroplane crash-landed in Italy and five more were forced down into the Mediterranean Sea by lack of fuel. In all, 24 bombers were lost and more than 60 of the 122 survivors landing in Tunisia had suffered battle damage.

Williams’s 1^st Bombardment Wing comprised nine B-17 bombardment groups. Previously, because of this large number of groups, provisional combat bomb wings had been created in April to control the groups tactically during large missions. To achieve a maximum effort against Schweinfurt, the 1^st Bombardment Wing, with sufficient aircraft and crews to employ four wing-sized boxes, formed provisional groups as well as wings, accomplished by eight groups providing a squadron or spare aircraft to form the composite groups needed to form a fourth combat wing. The Schweinfurt force in all had 230 bombers comprising 12 groups divided into two task forces, each with two wings, each wing composed of a three-group formation, and was more than 20 miles (32 km) in length. Williams led the mission, flying as co-pilot in an aeroplane of the leading formation, as wingman to the commander of the 91^st Bombardment Group.

The Schweinfurt task forces followed the same route as the Regensburg force. Because of the mission’s delayed start, eight squadrons of Spitfire fighters (96 British aircraft) of Air Vice Marshal H. W. L Saunders’s No. 11 Group and Air Vice Marshal W. F. Dickson’s No. 83 Group had been added to escort the Schweinfurt force as far as Antwerp, where P-47 fighters would take over and escort it to Eupen. The order for the mission specified that the B-17 bombers were to fly at altitudes between 23,000 and 26,500 ft (7010 and 8075 m), but approaching the coast of the Netherlands at 13.30, it was confronted with developing cloud masses not present earlier in the day. The commander of the first task force estimated that the bombers would not be able to climb above the cloud and elected to fly under it at 17,000 ft (5180 m), increasing the vulnerability of the bombers to fighter attack.

The first German attacks began almost immediately, and employed tactics different from those employed against the morning mission. The leading wing was tackled continuously in head-on attacks by both Bf 109 and Fw 190 fighters, and although the British escorts claimed eight victories they were forced to return to base early in the engagement. The two groups of P-47 fighters (88 aircraft) arrived five and eight minutes late, and despite some individual combats, they too were forced to break off almost as soon as they arrived.

Inside German airspace, the Bf 109G-6 fighters of the 5 Staffel of Major Anton Mader’s Jagdgeschwader 11, which had pioneered the fitment of the Werfer-Granate 21 unguided air-to-air rocket weapon system to the Luftwaffe’s single-engined day fighter force on only the preceding day, as well as the similarly armed rocket-launching Bf 110 twin-engined heavy fighters, including some night-fighters, joined the battle as more than 300 fighters from 24 bases opposed the raid. At 14.36 the force diverged from the morning’s route at Worms, thereby alerting the German defenders to the fact that the target was Schweinfurt. Losses among the 57 B-17 bombers of the lead wing were so severe that many among its airmen considered the possibility that the wing might be annihilated before reaching its target. However, 15 miles from Schweinfurt, the opposing fighters, after shooting down 22 bombers, disengaged and landed in order to refuel and rearm in order to attack the force on its way out. Some 5 miles (8 km) from Schweinfurt, German Flak guns began firing an effective anti-aircraft barrage into the bomber force’s flight path.

At 14.57, some 40 B-17 bombers remained of the lead wing when it dropped its bombs on the target area containing five factories and 30,000 workers, followed over a 24-minute span by the remainder of the force. Each wing encountered increasingly thick smoke from preceding bomb explosions, and this was a major impediment to accurate bombing. A total of 183 bombers dropped 424.3 tons of bombs, including 125 tons of incendiaries.

Three B-17 bombers were shot down by Flak over Schweinfurt. About 15 minutes after leaving the target area, each task force circled over the town of Meiningen to reassemble its formations, then continued to the west in the direction of Brussels. At about 15.30 German fighters renewed their attacks, concentrating now on damaged bombers. Between 16.20 and 17.00, a covering force of 93 P-47 and 95 Supermarine Spitfire single-engined fighters arrived to provide withdrawal support, claiming 21 fighters shot down, but eight more bombers were lost before the force reached the North Sea, in which three more crash-landed. The Schweinfurt force lost a total of 36 bombers.

The 8^th AAF listed 55 of its bombers with 552 men as missing after the August 17 double-target mission. About half of the latter became prisoners of war, and 20 were interned in Switzerland. Some 60 aircraft were lost over German-controlled territory or in Switzerland, or ditched at sea, with five crews rescued. Seven men were killed in bombers returning to base after completed the mission, and 21 men were wounded.

The 60 aircraft lost on a single mission more than doubled the highest previous loss at that time. Moreover, 55 to 95 additional aircraft had been badly damaged. Of those damaged, many were stranded in North Africa and never repaired. Three P-47 fighters of Colonel Hubert A. Zemke’s 56^th Fighter Group and two RAF Spitfires were shot down attempting to protect the Schweinfurt force.

Spitfire pilots claimed 13 German fighters shot down and P-47 pilots claimed 19. Gunners on the bombers claimed 288 fighters shot down, but Luftwaffe records show that only 25 to 27 fighters were lost.

In Regensburg, all six main workshops of the Messerschmitt factory were destroyed or severely damaged, as were many supporting structures including the final assembly line. In Schweinfurt, the destruction was less severe but nonetheless extensive. The two largest factories, Kugelfischer & Company and Vereinigte Kugellager Fabrik I, suffered 80 direct hits. About 380,000 sq ft (35000 m²) of buildings in the five factories were destroyed, and more than 1 million sq ft (100000 m²) suffered fire damage. All of the factories except that of Kugelfischer had extensive fire damage to machinery when incendiaries ignited the machine oil used in the manufacturing process.

Albert Speer, the German minister of armaments and production, reported an immediate 34%reduction in production, but both the production shortfall and the actual loss of bearings were compensated by extensive surpluses found throughout Germany in the aftermath of the raid. The industry’s infrastructure, while vulnerable to a sustained bombing campaign, was not vulnerable to destruction by a single raid. Speer indicated that the two major errors made by the USAAF in 'Double Strike' were first the division of their force instead of a concentrated attack on the ball-bearing plants, and second their failure to follow the first attack with more air assaults.

Some 203 German civilians were also killed in 'Double Strike'. While the battle resulted in a German victory, the scale and range of the US operation, together with the British 'Hydra' against Peenemünde on the same day, shocked the German air command, and the stress contributed to the suicide of the Luftwaffe’s chief-of-staff, Generaloberst Hans Jeschonnek, on the following day.

The Schweinfurt mission in particular presaged the failure of deep-penetration air raids on Germany without adequate long-range escort. The 1^st Bombardment Wing was over German-occupied territory for 3 hours 30 minutes, of which 2 hours 10 minutes, including all of the time spent over Germany itself, saw no fighter support whatsoever. When the second attack on Schweinfurt was delivered on 14 October, the loss of more than 20% of the attacking force (60 out of 291 B-17 bombers) resulted in the suspension of deep raids for five months.