Throughout the latter half of the 1930s and into the early 1940s, the Junkers Ju 87 "Stuka" dive bomber asserted itself as one of the more feared German Luftwaffe aircraft in the skies over Europe. The type was used to great effect in the German assaults against Poland, Norway, the Low Countries and France before attention turned to the invasion of Britain. It also played a role in the German invasion of the Soviet Union through Operation Barbarossa to begin the "East Front" as well as strikes against targets in North Africa and across the Mediterranean Theater. While the type proved itself more that capable for its intended role, its effectiveness waned in the wake of direct combat with intercepting enemy fighters serving to showcase its obvious vulnerabilities on a grand stage - particularly during the Battle of Britain in the summer of 1940. As it stood, the Ju 87 was a slow, unmaneuverable mount with severely limited defensive capabilities.
As such, the Junkers concern was charged with development of a similar-minded modern dive bomber, incorporating some of the excellent qualities inherent in the Ju 87 system. Key to this was retaining the two-man crew arrangement (including the rear gunner) and the identifiable inverted "gull-wing" wing design (sporting both anhedral and dihedral angles). A new fuselage design was drawn up which utilized a sloped frontal section offering up improved downward views over the engine mounting. The cockpit was centralized along the fuselage dorsal spine and a tapered empennage employed. Both the wings and fuselage would be called upon to bear the brunt of the intended bomb load. As in the Ju 87, the new design would make use of a rear gunner to defend the aircraft's vulnerable "six" region. A three-bladed propeller would be powered by a front-mounted Junkers Jumo 213A series 12-cylinder inverted-vee inline piston engine rated at 1,776 horsepower (this engine already in production and serving Focke-Wulf Fw 190 fighters and Junkers Ju 88 bombers). Overall dimensions included a wingspan of nearly 60 feet with a running length of 38.8 feet. The two crew would be seated in tandem (back-to-back) under an enclosed, framed cockpit. Armor would feature into the design to help protect the crew, engine and fuel stores from low-lying threats. The fuselage would be constructed of an all-metal substructure and skin.
Proposed fixed armament became a pair of 20mm MG 151/20 series cannons firing from the wing roots. Additionally, a 13mm MG 131 series machine gun as well as a 15mm MG 151/15 series cannon would be mounted to a dorsal turret at the rear. In terms of bomb load, the Ju 187 would be expected to carry a 1,100lb bomb along its fuselage centerline as well as smaller diameter bombs underwing for a most impressive and well-armed dive bomber design.
Key refinements greeted the new aircraft which was ultimately assigned the designation of "Ju 187". Unlike the Ju 87 before it, the Ju 187 was to be completed with a retractable undercarriage to help increase airflow and improve aerodynamics. This was of a traditional configuration involving two main landing gear legs and a tail wheel. One of the more ambitious aspects of the Ju 187 design was to be its "rotating" tail section which, when fixed in place, acted as a normal empennage unit. However, the rotating nature of its design would allow the tail section to point the vertical tail fin downwards (preserving the horizontal tail planes), allowing for unfettered views of oncoming enemy from the rear gunner's seat - thusly providing for an unobstructed firing arc and improving self-defense capabilities of the aircraft.
Work on the project was begun and wind tunnel testing on several model forms was underway. A full size mockup was also under construction when, in 1943, the Reich Air Ministry canceled the Ju 187 project. Apparently, the projected maximum speed of the fully bomb-laden aircraft was never expected to exceed that of the existing Ju 87s in service by much and, when coupled with the technological barrier presented by the rotating tail unit, the program projected too many questions to allow for further funding and development. The Ju 187 project was further hindered by the fact that the Messerschmitt Bf 109 and Focke-Wulf Fw 190 fighters - available in larger quantities by this point in the war - had been successfully converted to capable dive bombers in their own right, thusly negating the need for a new, costly and dedicated dive bomber design.