During the war, the need to produce self-propelled anti-aircraft guns capable of protecting troops against low-flying air attacks became marked. To this end, the hull of the Panzer IV medium tank, the Flakpanzer IV Wirbelwind, was used as a platform to add on a 20 mm Flak 38 quadruple gun system. By the end of 1944 the Wirbelwind was joined by the more powerful Ostwind, which was mounted with a 37 mm Flak 43 anti-aircraft gun. Providing a greater range of fire, the anti-aircraft armament protected by a thick and characteristic shield mounted on an "open-roof" hexagonal turret, the Ostwind could also be effectively deployed against ground targets in close support of troops on the battlefield. The few "Ostwind" that were produced were delivered to the anti-aircraft units of the Panzer Division, and proved very effective on operations.