Messerschmitt Bf 110 D-2 piloted by Walter Rubensdörffer, Gruppenkommandeur Erprobungsgruppe 210, in Calais-Marck, the 15th August 1940.

The practice of incorporating low-weight bombs to aircraft dates back from the First World War and was of common utilization during the Spanish Civil War, specially in the Heinkel He 51 biplane fighters. However, it was not until the Second World War when serious efforts were made to develop combat techniques specific for bomb-carrying fighter aircraft. Until that moment the tactic had been to rely on an improvised support on the battlefield.

When the Battle of France ended, the Luftwaffe created a special unit, the Erprobungsgruppe 210, to put into service, in ostensible amounts, the Messerschmitt Me 210 fighter-bomber, which in that time was flying as prototype only. It seemed that the Me 210 could not be ready for months coming, so during 1940 the operations of the unit were carried out with two staffeln of the Me Bf 110 and one of the Me Bf 109. It was such the importance of this operation that the best pilots were assigned to it. The command was entrusted to Walter Rubensdörffer, a Swiss veteran from the Spanish Civil War.

Born in Basel the 1st August 1910, Rubensdörffer had served during some years in the Luftwaffe before the Second World War. He was an unconditional supporter of bombing practices as a help in the battlefield, tactic which he had successfully put into practice in the Condor Legion. Rubensdörffer received the command of the Erprobungsgruppe 210 from Albert Kesselring the 1st July 1940 and he reported that the unit was ready for combat ten days later. He led the first attack of ten Bf 110 based in Saint-Omer (France) against targets in the area of Harwich (England) the 10th July. Initially used as a long-range fighter, the Messerschmitt Bf 110 demonstrated to be an effective bomber as well.

During the following month, Rubensdörffer led the EGr 210 with notable success in 28 missions against targets designated in southern England, as well as against coastal vessels. Almost invariably the targets were reported as strongly protected or very difficult to surround by the units deployed by the Luftwaffe, with the result that the EGr 210 soon earned a reputation of elite unit. As example of those operations can be mentioned the attacks that Rubensdörffer performed upon the CH inner radar network in the southeast of England, the 12th August, when he led several carefully coordinated bombings against Dover, Rye, Pevensey and Dunkirk (in the north of Kent) without suffering losses. All the chiefs of the Schawarm in these attacks (Otto Hinze, Willhelm Rössiger and Martin Lutz) later entered the command of the EGr 210.

During the famous "Black Tuesday", the 15th August, Rubensdörffer had already led the bombings against the airbases of Martlesham and Manston separately, when he received, already on the afternoon, the order to attack the important Royal Air Force base at Kenley, after joining a escort of Bf 109 while in route to the target. Taking off with fifteen Bf 110 bombers and his own Staffel 3, equipped with eight Bf 109, Rubensdörffer set course to Kenley, but he missed the meeting with his escort.

Leaving the mantle of clouds south of London, he saw an airbase in front of him and attacked it. Unfortunately this one was Croydon, not Kenley, and in that very moment the 111th Squadron, commanded by Squadron Leader John Thompson, was taking off. Dropping their bombs, which caused considerable damages, Rubensdörffer and his pilots desperately tried to reach the safety that clouds provided, but they were chased and decimated by the Hurrican fighters. The aircraft of the oberleutnants Fiedeler and Habish, along with those of the lieutenants Kock, Beuel, Ortwer and Marx, fell in the subsequent minutes. It was Thompson who attacked Rubensdörffer and, after a long struggle trying to keep his Bf 110 in flight, the German leader crashed near Mayfield. He and his gunner, Feldwebel Richard Ehekercher, died ablaze.