The Flakpanzer IV "Ostwind" (East Wind in German) was a self-propelled anti-aircraft gun based on the Panzer IV tank. It was developed in 1944 as a successor to the earlier self-propelled anti-aircraft gun Wirbelwind. The Panzer IV's turret was removed and replaced with an open-top, hexagonal turret which housed one 3.7 cm FlaK 43. In addition to its intended role as an anti-aircraft weapon, the fast-firing gun was highly effective against light vehicles and minor fortifications. A closed-top design would have been preferable, but this was not possible due to the heavy smoke generated by the gun. Production of the vehicle was carried out by Deutsche Eisenwerke at Duisburg.