Reduced activity again with only one large fighter sweep during the afternoon. German invasion cancelled indefinitely.
Night: Heavy attacks against London. Merseyside and Glasgow also raided.
Weather: Squally showers with thunder and bright intervals.
Unternehmen Seelöwe Cancelled Indefinitely
On the morning of 17 September 1940, a critical shift occurred in German strategy. While Luftwaffe commanders were preparing the day’s air operations, a directive arrived from Hitler’s headquarters that fundamentally changed the course of the war. Unternehmen Seelöwe—Operation Sea Lion, the planned German invasion of Britain—was formally postponed once again, this time indefinitely. The order, issued under Hitler’s direct authority, instructed German forces to begin dismantling the infrastructure required for an airborne invasion, including the withdrawal of air-loading equipment from Dutch airfields. Radio intercepts, monitored by the Ultra decryption team at Bletchley Park, captured the message in real time. Marshal of the Royal Air Force Sir Cyril Newall, informed by the intercepts, advised the Air Ministry that, with the worsening autumn weather and the Luftwaffe’s inability to establish air superiority, the threat of invasion was effectively over for 1940. Hitler’s new directive suggested that the invasion could still be staged in October, but only under ideal weather and air conditions—an increasingly unlikely prospect. In truth, the removal of logistical support from forward airfields confirmed what the Royal Navy and Fighter Command had already begun to suspect: Germany’s invasion had been shelved.
Enemy Action by Day
The morning hours brought little in the way of offensive activity from the Luftwaffe. Patchy squalls and thunder disrupted visibility across the Channel, and radar plots detected only scattered signals—most of which appeared to be single aircraft operating independently. These were believed to be weather or photographic reconnaissance flights and were not engaged by Fighter Command. One German bomber flew close to the town of Dover, prompting an air raid alarm. After briefly tracking the coastline, it turned away and returned to base. Fighter Command, interpreting the morning quiet as a temporary pause rather than a strategic shift, kept its squadrons at readiness but refrained from mass interception.
Interception Near Filton: Ju 88 Brought Down
By midday, the Luftwaffe launched a minor probing attack. A formation of Junkers Ju 88 bombers was detected flying north from the Portland area, seemingly heading towards industrial targets in the Bristol region. Spitfires of No. 152 Squadron were scrambled from Warmwell and vectored to intercept the formation. In the engagement that followed, one Ju 88 was heavily damaged and pursued as it attempted to escape northeast. The aircraft was finally brought down near Warminster, southeast of Bath. The German pilot was killed in the crash, while the three surviving crew members were captured. Among them was a Gruppenkommandeur—his loss marking a significant blow to the Luftwaffe’s tactical leadership.
Afternoon Fighter Sweep Over East Kent
With conditions improving in the afternoon, a large-scale Luftwaffe fighter sweep developed around 15:30. Radar detected a formation of approximately 300 aircraft crossing the Kent coast between Lympne, Dover, and Deal. The leading formation—estimated at over 110 aircraft—penetrated as far west as Maidstone. Others spread across East Kent but did not cross the Thames Estuary. The Inner Artillery Zone was not penetrated. The Luftwaffe contingent included multiple Gruppen of Bf 109s from JG 26, JG 27, and JG 53, supported by a small number of Ju 88 bombers acting as bait. In accordance with Göring’s latest directive, the intent was to lure RAF fighters into combat without risking major bomber formations.
No. 11 Group scrambled 23 fighter squadrons to intercept the raid, with Hurricane and Spitfire squadrons launching from airfields across southern England. No. 12 Group also contributed five squadrons, patrolling the northern approaches to the Estuary at altitudes between 15,000 and 20,000 feet. Over the Kent countryside, intense dogfights broke out. Spitfires of No. 41 Squadron were heavily engaged near Dover, taking on a large Bf 109 formation. Several Messerschmitt Bf 109s were seen trailing smoke as they broke away from combat and attempted to disengage. Two aircraft crashed into the Channel and were lost, while a third came down near Deal. Two others, heavily damaged, managed to return across the Channel and land at Wissant.
The combat was not without its loss. Flying Officer J.G. Boyle’s aircraft was hit over Manston and forced to return to Hornchurch. Pilot Officer J.N. Mackenzie’s Spitfire was severely damaged and crash-landed beyond repair, although he emerged unhurt. Pilot Officer H.C. Baker was forced to land at Stelling Minnis after sustaining damage in a dogfight, and P/O H.H. Chalder was also forced to withdraw from action.
Heavy Fighting Over Mid-Kent
Further north, Hurricane squadrons including Nos. 17, 303, 501, 504, and 607 engaged enemy formations near Ashford and Gatwick. No. 501 Squadron suffered the loss of two Hurricanes in the engagement. Sgt. J.H. Lacey bailed out of his aircraft and survived. Sgt. E.J. Egan was killed when his Hurricane was engulfed in flames and crashed. One confirmed Luftwaffe victory was credited to Hauptmann Wolf-Dietrich Wilcke of Stab III./JG 53, who claimed a Hurricane near Ashford. Hauptmann Eduard Neumann of Stab I./JG 27 claimed two further victories over the Gatwick area.
Spitfires of No. 19 Squadron also entered the fray over North Kent. Sub-Lieutenant Tony Blake, on secondment from the Royal Navy, accounted for two Bf 109s during the battle, making him the Navy’s top-scoring fighter pilot to date. Among the Luftwaffe losses was Oblt. Jakob Stoll of 9./JG 53, missing in action and presumed dead. With fourteen confirmed victories, he was a significant loss. Another Bf 109 pilot, Uffz. Karl-Heinz Bock of 7./JG 26, suffered engine failure and force-landed near Rye, becoming a prisoner of war.
Later in the afternoon, around 18:00, Hurricanes from No. 151 Squadron, operating from RAF Digby, intercepted a Heinkel He 111 over southern England. The bomber was damaged and forced to return towards France, possibly failing to reach base. The engagement confirmed that scattered bomber probes were still underway despite the reduced scale of daylight operations.
Enemy Action by Night
At approximately 20:00, the Luftwaffe began a new night assault on Britain, continuing the pattern established on the 16th. Initial formations were detected crossing the coast from Cherbourg, Seine Bay, and Dieppe. The majority of these raids consisted of single aircraft flying at medium altitude, although larger groupings were observed moving towards London. The capital endured continuous bombing through the night. Aircraft from III./KG 27 were among the first to arrive, dropping high-explosive bombs in the midnight raid. The city of Liverpool was also targeted, with raids extending into Merseyside and the South Wales industrial corridor. Junkers Ju 88s from unspecified units conducted raids on Merseyside, while Dornier Do 17s of KGr 606, flying out of Brest, bombed targets in and around the Liverpool docks.
Many bombs landed indiscriminately. While dock facilities were clearly targeted, residential districts once again bore the brunt. Entire streets were damaged or destroyed, and civilian casualties mounted. The cities of Newcastle and Durham were also struck. One high-explosive bomb fell in an open field between Southbrook Farm and Catcote Farm, near West Hartlepool, injuring two cattle and damaging farm structures. The incident was typical of many bombs dropped far from intended targets due to navigation errors, weather conditions, or hasty releases under anti-aircraft fire.
Introduction of the 1,000 kg Parachute Bomb
During the night, the Luftwaffe introduced a new weapon in its campaign of terror: the 1,000-kilogram parachute mine, adapted from sea ordnance. These massive blast bombs, measuring approximately eight feet in length and two feet in diameter, were dropped with a silk parachute to reduce velocity. Upon impact, they created immense concussive blasts, destroying buildings over a quarter-mile radius and shattering windows more than a mile away. Several were dropped over Kent, London, and Essex. Many failed to detonate and posed a significant hazard. The Admiralty advised all personnel to avoid metal objects and vibrations near suspected impact sites due to the bombs’ magnetic triggers.
Civilian Heroism and Destruction on the Ground
In one notable act of bravery, Auxiliary Fireman Harry Errington rescued two trapped colleagues from the wreckage of a building that had taken a direct hit while being used as a shelter by fire crews. For his actions, Errington was later awarded the George Cross. Fires broke out in several locations across London. Major blazes required the deployment of twenty or more pump units in Bermondsey, Old Kent Road, Poplar, and Lewisham. Fires at the Millwall and East India Docks were contained after several hours. On Oxford Street, the department stores D.H. Evans and John Lewis were hit, requiring forty and thirty pumps respectively. The Greenwich telephone exchange was struck directly, although staff survived in the shelter below. Siemens Works in Woolwich was also hit, with fires reported shortly after midnight.
Liverpool sustained heavy damage between 19:43 and 23:50. More than two dozen fires were started, including major outbreaks in dock areas and residential districts. In Caterham, five high-explosive bombs fell at 08:50, destroying a food store and a private residence. In Portsmouth, a 13:21 bombing caused fifteen casualties and damage to a church and water mains. At 15:05, a lone aircraft attacked the Rootes Factory at Speke. Though two houses were hit, the factory escaped damage and no injuries were reported.
Summary
The air battles of 17 September resulted in eight German aircraft being destroyed or lost in action with 14 airmen killed or missing. RAF Fighter Command also lost six aircraft with three pilots killed. While the Luftwaffe failed to achieve air superiority, its shift to night operations was increasingly effective at inflicting material and psychological damage. However, the withdrawal of support for Operation Sea Lion marked a strategic turning point. The invasion threat had been deflected. The war in the air would continue—but now, increasingly, under cover of darkness.
German Losses:
Airmen: 14 | Aircraft: 8
British Losses:
Airmen: 3 | Aircraft: 6
Hurricane P3820, No. 501 Squadron
Sgt E.J. Egan killed. Shot down in sudden attack by Bf 109. Aircraft burst into flames. Pilot did not bale out.
http://www.bbm.org.uk/airmen/Egan.htm
Hurricane P3933, No. 607 Squadron
Sgt J. Lansdell killed. Shot down during combat with Bf 109. Failed to bale out.
http://www.bbm.org.uk/airmen/Lansdell.htm
Hurricane V7529, No. 504 Squadron
Sgt D.A. Helcke killed. Lost control during attacking practice and failed to bale out.
http://www.bbm.org.uk/airmen/Helcke.htm
Photo Descriptions
- A wide view of the bomb-damaged shell of the John Lewis department store on London’s Oxford Street, following an air raid on 17 September 1940.
- Shop mannequins are among the debris that litters the pavement outside the John Lewis department store on London’s Oxford Street, following an air raid on London. Windows have been blown out and awnings damaged.
- A scene of devastation in the Docklands area of London attacked by German bombers on 17 September 1940.