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Flakpanzer Coelian was a self-propelled anti-aircraft gun design by Rheinmetall during World War II for the German armed forces. It was intended to be armed with two 3.7 cm FlaK 43 gun in a fully enclosed, rotating turret on the hull of a Panther medium tank but was not built before the end of the war in Europe.
In the first years of the war, the Wehrmacht had less interest in developing self-propelled anti-aircraft guns, but as the Allies developed air superiority, the need for more mobile and better-armed self-propelled anti-aircraft guns increased. The Wehrmacht had adapted a variety of wheeled and half-track vehicles to serve as mobile forward air defence positions to protect armour and infantry units in the field as well as for temporary forward area positions such as mobile headquarters and logistic points. As Allied fighter bombers and other ground attack aircraft moved from machine gun armament and bombing to air-to-ground rockets, the air defence positions were even more vulnerable. The answer was to adapt a tank chassis with a specialized turret that would protect the gun crews while they fired upon approaching Allied aircraft.
As a consequence, the German Army High Command issued a demand for an anti-aircraft tank based on the chassis of the Panther tank design. Rheinmetall developed "Coelian" in various versions, including one with four 20mm MG 151/20 guns, but kept having to revise designs based on changing government requirements (such as demands for more modern guns with longer barrels). Eventually, in May 1944 a turret with a single 5.5 cm gun was developed, together with another with twin 3.7 cm FlaK 43 guns.
However, it soon became clear that no chassis would be available for Flakpanzers for a variety of reasons, including the Allies' landing in Normandy, the increasing Allied strategic bombing offensive, and raw material shortages. By mid-February 1945, only a wooden prototype of the 3.7 cm turret model on a Panther D hull had been created.