The Flakpanzer IV Wirbelwind, or \"Whirlwind\", is a German self-propelled anti-aircraft gun from the end of World War II. It was built on the chassis of the most popular tank of the Third Reich - The Panzer IV. Production begain in November of 1944. The chassis of the older Panzer IV or newer versions, withdrawn from the front for repairs, were rebuilt. The traditional turret was replaced by a polygonal open turret equipped with a 20mm Flak 38 quadruple anti-aircraft gun. The rotating turret turn