Panzer II variants the Pz.Kpfw. IIJ, it was redesigned after the Panzer V Panther, most noticeably with the introduction of fully sloped frontal armor. Two versions were initially planned, a lighter, faster 18-ton variant and a slower, 26-ton vehicle; the former was abandoned at an early stage. Subsequently, work on the first prototype was abandoned when it was determined that the vehicle was underarmed for its weight, and versions of the Panzer IV and V could serve just as well in the reconnaissance role while being more capable of defending themselves. This vehicle never received an official Panzerkampfwagen title, but it would have
AI Mk. IV radar be flying by. Instead, they had one of the workers bicycle along a nearby cliff carrying a small plate of aluminum sheet. This neatly demonstrated its ability to detect objects very close to the ground. As AIS rapidly developed into the AI Mk. VII, development of the Mk. IV's follow-ons, the Mk. V, and Mk. VI (see below) saw vacillating support. Considerable additional development of AIS was required, with the first production version arriving in February 1942, and subsequently requiring an extended period of installation development and testing. The first kill by a Mk. VII set was on the night