226: Adlertag

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This episode of History of the Second World War delves into the pivotal moments of the Battle of Britain, focusing on the Luftwaffe’s final preparations and the critical operations of Adlertag (Eagle Day), the code name for the Luftwaffe’s intensified campaign to neutralize RAF Fighter Command and secure Germany’s invasion plans. As the conflict escalates, the podcast explores the high-stakes strategies, key decisions, and relentless aerial battles that defined this turning point in the war, offering listeners a gripping look at the chaos and courage of this historic clash.

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Summary

This episode of History of the Second World War delves into the pivotal moments of the Battle of Britain, focusing on the Luftwaffe’s final preparations and the critical operations of Adlertag (Eagle Day), the code name for the Luftwaffe’s intensified campaign to neutralize RAF Fighter Command and secure Germany’s invasion plans . As the conflict escalates, the podcast explores the high-stakes strategies, key decisions, and relentless aerial battles that defined this turning point in the war, offering listeners a gripping look at the chaos and courage of this historic clash. Hello everyone and welcome to History of the Second World War Episode 226 - The Battle of Britain Part 1 - Adlertag. This week a big thank you goes out to John and eheminger for supporting the podcast by becoming members. Members get access to ad-free versions of all of the podcast’s episode plus special member only episodes roughly once a month. Head on over to historyofthesecondworldwar.com/members to find out more. Over the course of the past 17 episodes the podcast has tracked the evolution of German plans for an invasion of Britain, and the efforts made in Britain to prevent that invasion from being successful. For the Luftwaffe, everything was leading up to one moment, the one day when they would begin their operations specifically designed to destroy the RAF, to prevent it from being an effective tool against the invasion. On 2 August Goering would publish his Preparations and Directives for the operation and they would include: the neutralization of RAF Fighter Command through aerial attrition and attacks on their air fields in Southern England; the destruction of the RAF resources that could be used against the invasion fleet; the neutralization of Royal Navy units in ports along the southern coast of England; and the night bombing of communications, logistics, and aircraft manufacturing targets throughout Britain. The day on which the operation began would be given a code name, Adlertag, which when translated means Eagle Day. After a few delays the date for Adlertag would be set to August 13th, the beginning of the third phase of the Battle of Britain. This would be the critical phase during which the RAF was fighting for its life, and it would continue to do so with a few weather related breaks until September 15th. This episode will cover the final days of preparations for Eagle Day, then the first two days of escalated activity August 12th and 13th. These two days would represent the first days of maximum effort for the Luftwaffe, after weeks of smaller scale attacks on various targets. They would also be critical days for the Luftwaffe because, if they wanted to achieve their goals tempo was critical. Sea Lion had to take place before the end of September, and so the Luftwaffe would only have a month, but the Luftwaffe leaders believed they had plenty of time.

After over a month of preparations, on August 13th the Luftwaffe’s attacks on the RAF in preparation for the German invasion would begin. They would have just a month to achieve their lofty goals. Importantly for the course of the fighting over the next 2 months, also present on that list were the Chain Home radar stations, which the Germans referred to as the DeTe devices, that were positioned to war the RAF of incoming German air raids, even though the Luftwaffe was aware of the stations themselves as well the fact that the British had some form of early warning system in place. This was proven by the radio signals that were intercepted over the course of the preceding weeks that were clear indications that the British knew about German aircraft before they were within visual range. Once the date was set for Eagle Day, furious preparations continued to try to ensure that the Luftwaffe was ready for several hard days of operations. This episode will cover those final days of preparations, as well as the first two days of serious fighting, August 12th and August 13th. These two days would represent the first days of maximum effort for the Luftwaffe, after weeks of smaller scale attacks on various targets. And tempo was critical if the Germans wanted to achieve their goals in time, they only had at most a month before the invasion had to occur.

As with many operations during the Second World War, the final stages of the Luftwaffe plans for their air attack against the RAF came together quite late. There had been discussions and planning meetings during June and July but final decisions were not made until the first week of August, when Goering, the Luftwaffe staff, and the commanders of the three Luftflotten that would actually care out the operation came together in a multi-day conference to iron out the final details. The staffs of the Luftflotten had different ideas about the best course of action, and so most of the days during this conference were spent on just trying to bring together all of the available plans into one cohesive whole. At this time the Luftwaffe leaders believed that they could greatly reduce the combat capabilities of the RAF in just 3 days of hard operations. A major reason for this very optimistic timeline was the fact that the German estimates for British fighter numbers was around 500, while the actual number of British fighter aircraft was actually more than 700. When this underestimation of their opponent was combined with the overestimation of German capabilities, particularly the belief that the Me-110 would be able to contribute meaningfully to the fighting, the result was simply a very optimistic view of how quickly the RAF fighter groups could be suppressed. The final date for the attack, August 13th would not be decided on for a few more days due to how critical weather would be in the final decision. With air operations totally dependent on the weather, the goal of the Germans was to find a period of good weather that was at predicted to last for at least 4 days. This would give them time to achieve their goals against the RAF, with one day to spare. Weather reporting was available via German submarines and supply ships that were positioned in the Atlantic and their reports pointed to a good high pressure system moving through the Azores after August 10th, and in fact the 10th was originally set as the date for Eagle Day before it was pushed 3 additional days due to the weather that occur on the 10th. In the days before the operations the fighter and bomber group commanders would run a lengthy series of map exercises to make sure everybody from the aircrew up to the group commanders knew what was expected of them during the opening period of the attacks. Because while the best plans could be laid, what mattered was the performance of the German squadrons which would actually execute the attacks. They would pilot the almost 2,500 aircraft available for the operation, which included almost 950 bombers, over 325 dive bombers, over 250 Me-110 heavy fighters, and over 850 Me-109s. Each aircraft squadron, regardless of what they were were flying would have important tasks during the three days of fighting.

While the Luftwaffe leaders were doing their planning, the fighting at the front never really ended and throughout the first two weeks of August, on any day where good weather presented itself over the English Channel you could almost guarantee that there would be some clashes between the RAF and Luftwaffe. This included attacks on coastal shipping as well as shore facilities, much like the Luftwaffe had been executing for the previous 6 weeks. Some of these were quite heavy, for example on the August 11th, theoretically a rest day for the Luftwaffe before their big operations, fighting over Dover would see the RAF Fighter Command lose 31 aircraft, along with 5 bombers on other missions, and on that same day the Luftwaffe last 36. This is noteworthy because it is clear that Eagle Day, when it would occur, was not unique because it was the start of the fighting, simply that it represented a major increase in the scale of the number of total aircraft involved. On the British side, there was some confusion as to why the Germans had not launched a major air campaign . This ties partially back to pre-war estimates of how an air campaign might occur, with a major emphasis on major bombing efforts to start a war. On August 6th these questions even made it to into the Daily Mirror which ran the headline “Why Hitler has waited so long”. The article would also include a prediction that when it happened, the Germans would include night raids in their operations “this must be remembered: neither the Germans nor ourselves have yet solved the problem of intercepting bombers at night. In any raid, a number of planes are sure to get through the defences.". Which was honestly a solid bit of analysis from the Daily Mirror. Propaganda efforts on both sides were in full force as well during the weeks before the attack, with the British Ministry of Information trying to get as much information as possible about the mindset of the British people . Meanwhile the Germans were trying to influence that mindset as much as possible. I feel it is my duty as a podcaster, after how derisively I talked about the British leaflet dropping campaigns of 1939 to mention that the Germans also dropped some leaflets over Britain during the summer of 1940. In particular these were copies of Hitler’s last appeal to reason speech that he had given in July. Most of these just fell on the empty countryside, and most of them were gathered up and destroyed, but I thought it was important to point out that the Germans were just as likely to fall into delusions of an easily swayed enemy as the British were.

While Eagle Day would be designated for August 13th, the 12th would end up being a very busy day as well. The British actually knew that the big Luftwaffe effort would begin on the 13th due to the decryption of Luftwaffe messages that used the Enigma system. The cracking of the Enigma, and the resulting information that was under the codename of Ultra is a very popular story from the Second World War. However, most of the emphasis of the famous work done by Turing and the others at Bletchley Park was for the Naval version of Engima. Each arm of the German military used the same type of Enigma machines, but they each had their own settings and their own procedures for using them, and the Naval procedures were much more secure. This resulted in the Luftwaffe messages being some of the easiest to break and decrypt. For example, they would intercept and decrypt Goering’s order of the day which would be sent to all of the squadrons of Lufflotten 2 and 3 which included “You will proceed to smash the British Air Force out of the sky.”. This allowed Dowding and the other British leaders to know that the 12th was not the start of the main German effort, but they would not be blamed for thinking that it was. The primary focus of the attacks on the day were the radio direction finding stations, Portsmouth harbor facilities, and then the Chain Home radar stations.

The attacks on the radar and RDF stations were a textbook example of what would today be called a suppression of enemy air defenses or SEAD mission . The goal was to hamper the early warning systems of the enemy to make the following days attacks more successful. For some of the attacks on the radar and RDF stations what could be considered precision bombers, or at least as precise as bombers got during the early parts of the war, were used. These were specifically fitted Bf-109s and Bf-110s that had set up to be bombers, carrying up to 250 kilograms of bombs. The squadrons of these single engine fighter bombers were highly skilled and hand picked for their abilities. The hope was that these bombers would have the speed and maneuverability to drop their bombs with more precision through the use of low altitude bombing runs executed in a shallow dive, which when targeting the air defense towers was an important factor. The theory had already been tested in mid-July in some air raids on July 13th, but August 12th would be a much greater test. Their targets were the stations at Dover, Ventnor, Pevensey, Rye, and Dunkirk which just west of Canterbury. In all cases they were able to drop some bombs on their targets and disable them, at least temporarily. Knocking the stations offline created a gap in the coverage of the radar, which was exactly what the Luftwaffe was aiming for. 63 Ju-88s were already on the way bomb the naval dockyards in Portsmouth which did serious damage to the railway station, the pier, and the several nearby buildings. Although fortunately no ships had been hit by the attack. Other Chain Home stations would pick up the Portsmouth raid before it reached its target but it was too late. While this was seen as a success, there was a greater problem for the Luftwaffe that was apparent by the middle of the afternoon on the 12th. The Germans began picking up new radio signals from all of the targets they had attacked earlier in the day. All but one of the targets were back online within a few hours, after repairing the largely superficial damage that they suffered. The only station that would stay offline for a longer period of time was Ventnor, and even there the British had brought in a mobile radio transmitter to make it seem like the station was back online. The rapid repair of the radar and direction finding stations would have an important impact on the Germans, and this would be a trend every time they made and effort to attack these areas. They would prove to be very difficult not to take offline, but to keep offline for any meaningful period of time. This meant that a lot of effort had to be expended for a very temporary benefit. The theory behind the fighter bombers was fully proven though, and their ability to fly in at high speed and low altitude, and then drop their bombs with reasonable precision would be an important ability for the Luftwaffe in the weeks ahead.

Another target for the Luftwaffe on the 12th, just like it would be over the following weeks would be attacks on airfields. One raid of Dornier bombers would attack the Lympne airfield, dropping 90 50 kilogram bombs on the airfield, most of which would fall on the airfield support facilities. And that would be just one of several raids on airfields throughout the day. Often the British fighters would be in the air to meet them, like with the case of 610 squadron from Biggin HIll that attacked the German formations over Lympne but they were set upon by Bf-109s that were escorting the bombers. But this was not always the case, and even when they were there were often still aircraft on the ground that made perfect targets for the German bombers. For example in a raid on Manston two Blenheims were destroyed, while 20 fighters were lost in the fighting above the airfield. With all of the different airfield raids for the day, none of them caused long term damage to the airfields, and in all cases the runways were repaired by the end of the day. Damage to support facilities would take a bit more time though, time that they often would not have before they were visited by bombing raids the next few days.

Given all of the actions on August 12th it is understandable if you consider it sort of an Eagle Day Part 1, and already on the 12th there were a few important themes that would play out over the following weeks. The first was the general inability of the Luftwaffe to cause permanent damage to the targets they were bombing. The two most important would be airfields and radar stations, both of which would prove to be far more difficult to cause serious damage to than the Germans expected. The second would be the problems that the fighters of Fighter Command would cause for the Luftwaffe formations during their bombing raids. There would be an insolvable problem for the German bombers and fighters, because if the fighters wanted to be the most effective at engaging and destroying Spitfires and Hurricanes they needed as much freedom as possible. This would allow them to position and attack in ways that gave them the greatest advantage. But this also required that they not be tightly tied to the bomber formations, and when they were not the bombers were very vulnerable to attacks by RAF fighters. The tension between these two priorities, destroying the RAF and protecting the bombers would be a major discussion point on the Luftwaffe side for the rest of the campaign. The third theme would be the ability of the RAF to bounce back from damage quickly. If they wanted to be successful in the campaign the RAF had to be able to take the German attacks and then be prepared for the ones the next day, and this meant being prepared to repair damage to infrastructure as well as to aircraft and pilots. Even before Eagle Day the chief of Fighter Command, Dowding, was deeply concerned about the ability of pilots, with major concerns that the pipeline of pilots was simply insufficient to the task. However, the group that would step forward to fill in this problem in the immediate future would be all of the non-British pilots that had made their way to Britain, the Czech, Polish, Belgian, French, and pilots of other nationalities. More aircraft were also arriving, and the best preparations were being made to ensure that facility repairs could be completed, but it was not yet known if these preparations would be sufficient.

When Eagle Day had been delayed until August 13th the plan had been to start the major air raids as early in the day as possible. The original plans would have seen the first bomber formations crossing over the channel before 6:30 in the morning. But then when the crew and pilots began to wake up in the morning, there was a problem, a cold wet fog was covering most of the German airfields and on both sides of the channel was a low thick cloud layer that would make ground attacks almost impossible. After some discussion the decision was made to delay the initial raids until later in the day, but there was a problem, because of the time it took to officially delay the start of the day some squadrons had already taken off. Without orders to the contrary many squadrons had taken off, under the assumption that they were still flying the planned raids and that maybe the weather just got better as they went. This meant that instead of the feeling of one massive raid the entire day would be disjointed, with a few squadrons from Luftflotte 2 still going forward with their missions while Luftflotte 3 did not even receive a delay order at all. Not a great start to what was supposed to be a highly orchestrated maximum effort series of missions. In Kesselring’s Luftflotte 2 one of these squadrons would be KG-2 which would not receive the radio messages to turn back, even though their Bf-110 escorts did actually turn back to the base and left the bombers on their own. The Dornier bombers of KG 2 were supposed to bomb Eastchurch airfield, and so on they went. The good news for the German bombers crews was that they largely caught the British unprepared, and due to some mistakes made when it came to getting squadrons airborne and in the right place to intercept them they were already over the airfield before being engaged by British fighters. Overall they would drop almost 500 bombs from around 500 meters causing serious damage to the airfield’s support buildings, including a large ammunition storage building and 5 Blenheims of coastal command. 3 squadrons of British fighters would then intercept the German bombers on their way away from the target, downing 5 of the German bombers. Sperrle’s Luftflotte 3, which was stationed further west than Luftflotte 2 would not receive the postponement order at all and so its early morning raids would go forward as planned. Their primary target was the Portland naval base with a combination of Ju-88s and Stukas ordered to bomb the naval facilities while being protected by almost 175 Bf-109s and 60 Bf-110s. During this raid the plan was for the Bf-109s to be ahead of the raid to sweep any fighters that they ran into while the Bf-110s were stationed closer into the bomber formations. The raid would end up being quite disappointing for the exact reasons that Luftflotte 2’s actions had been postponed. When the Stukas were out of the channel it was clear that the clouds beneath them were solid and unbroken and so very shortly after they arrived over Portland they just turned around and returned to their airfields. Not exactly safe to try and dive bombing through clouds. The Ju-88s stuck around a bit longer in the hopes that there would be some breaks in the clouds but these breaks never developed and eventually they also turned for home, having dropped none of their payloads. To make the aborted mission even worse on the way back to France they were intercepted by Hurricanes and 4 Ju-88s were shot down.

After many hours of delays due to the weather Luftflotte 3’s afternoon raids began to form up over land before striking out over the channel for their targets. 58 Ju-88s were designated to attack three different RAF airfields while 52 Stukas attacked two others. There was also a bit of a game afoot with these raids because before they were detected by British radar there was another group of aircraft sent forward, 23 Bf-110s which were designed to be basically bait for the RAF fighters. The Bf-110s seemed to be headed to Portland, and due to the fuzziness of radar at this time, and the size of the Bf-110s their formation was mistaken for a bombing raid. The good news is that this caused the distraction to work, and the RAF moved to intercept, the bad news is that this also meant that the Bf-110s would be met by three squadrons of Hurricanes . While this achieved the goal of the flight, it also meant that suddenly the Bf-110s had to deal with three squadrons of Hurricanes who were very prepared to meet them. It was something of a disaster, and would be an early example of many of the problems that the German heavy fighter would have in the skies over Britain. They did manage to shoot down one Hurricane and damage a few more but in return 7 Me-110s were shot down and another seven were damaged. To make matters even worse, after this sacrifice was made, the Ju-88s were not even able to bomb their actual targets, the airfields. Instead, the bombers once again encountered heavy cloud cover and so they diverted the raid to Southampton where the target was a bit larger than just an airfield. Due to this late change in direction the German bombers avoided all attempts to interception and were able to drop their bombs and head back across the channel without incident.

While the Bf-110s would experience some challenges, similar issues would be experienced by the Stukas on Eagle Day. Their raids would be against a few RAF airfields and in these afternoon raids the weather actually was good enough for the bombing to actually occur. As would happen from time to time, some of the British fighter pilots that moved in to intercept this raid found themselves hearing a series of strange voices, with the two groups of aircraft having, by pure coincidence, selected similar radio frequencies. The fighting that ensued had the same character as many of the melees during these August days. The German bombers, in this case Stukas, were desperately trying to just get to the point where they could drop their bombs and go home. The German fighters, both 109s and 110s were trying to protect the bombers while also attacking the arriving Spitfires and Hurricanes. In the resulting fighting about a 1/3 of the Stukas would be lost, along with of course all of their crews. Other Stuka squadrons would have similar experiences during the day. But then there were also moments where the Stuka performed very well, if a Stuka raid could reach its target without being intercepted it would prove why it had been so feared during the land campaigns in Poland and France. Bombs could be delivered exactly on target to cause maximum damage, it was just a matter of being allowed to get them there and then getting out before British fighters arrived.

During the raids on various airfields one of the interesting new features that caught the British off guard was the use of air dropped mines. These came in the form of the SC 250 bombs which were dropped with a type 17 fuse. These fuses were designed in both a short and long delay variant so that they would land, not explode, but then were set to go off anytime up to 96 hours after they were dropped. These mines were often more of a problem than the actual bombs that were dropped because there were always staff ready and waiting for repair bomb damage, but dealing with an explosive that had not yet exploded was a much more challenging task. What was worse, the bombs proved to be very difficult to disarm, to the point where a least one bomb disposal unit was killed trying to disable one of the bombs. For several weeks all they could really do was mark the position of any unexploded mines and then wait until it was determined how they could be disabled. Within weeks there were unexploded bombs all over the place, including 62 within the perimeter of the Biggin Hill airfield. Even before proper disposal techniques were determined for the first wave of unexploded mines, the Germans further complicated their disposal by adding tumbler fuses so that they would also detonate if they were in anyway moved. The numbers of these bombs, which essentially functioned as land mines, would grow for the rest of 1940.

In total, on the first day of their big offensive, the Luftwaffe would sent out 1,484 sorties which seems like a lot but many of them did not actually achieve anything due to weather and cloud cover. What was worse was that what impact they did have was heavily exaggerated with the Luftflotten intelligence estimating that they had hit 9 different airfields with five of them being considered to have been put out of action. This could not have been further from the truth and in fact, of all of the airfields that actually had bombs dropped on them during August 12 and 13, none of them were out of action for more than a day. This would be a continuing issue for the Luftwaffe in its attempts both to plan further operations and to understand where it stood in terms of accomplishing its goal of greatly diminishing the combat capabilities of the RAF. They would constantly underestimate the resilience of the entire RAF Fighter Command structure from the airfield repairmen to the output of the British aircraft factories. The tendency of airmen to overcount victories just made everything worse, with the estimates for Eagle Day being a total of 70 Spitfires and Hurricanes and 18 Blenheims destroyed. This balanced acceptably against the Luftwaffe’s own losses of 47, with an almost 2 to 1 kill ratio which was not perfect but was within the acceptable limits. The problem was that the real number of RAF losses was 50 total aircraft, including the Blenheims, which meant that the Luftwaffe was maintaining only a 1 to 1 kill ratio. This was a much greater problem because even with the Germans underestimating total British strength a 1 to 1 ratio would make it almost impossible to both suppress the RAF and have enough aircraft left over to support the invasion. It is worth remembering that the optimistic German estimates for total Fighter Command strength were between 300 and 400, and if 70 of those had been destroyed in one day! A week is all it would take they had destroyed over one quarter of them in a single day, and it had been a bad weather day. With jubilation the Luftlotten staffs were already planning the next day of operations, with the only downer being that the weather forecasts for the 14th were not good and so operations might be hampered for the second day in a row. But now that the major effort had started, all they could do was continue forward, and so they would. We will do the same next episode, the August 14th to August 18th, also known as the Hardest Day