Panzer III addition, to counter enemy anti-tank rifles, starting from 1943, the Ausf. L version began the use of spaced armour sideskirts and screens (known as "Schürzen" in German) around the turret and on the vulnerable hull-sides. However, due to the introduction of the upgunned and more-armoured Panzer IV, the Panzer III was, after the German defeat at the Battle of Kursk in the summer of 1943, relegated to secondary/minor combat roles, such as tank-training, and it was finally replaced as the main German medium tank by the Panzer IV and the Panzer V Panther. The Panzer III's strong, reliable and durable
AI Mk. IV radar looking up from the display at the last minute, and the system was used only experimentally. By this time the microwave units had started to arrive in small numbers, so Mk. V production was repeatedly delayed pending their arrival, and eventually cancelled. Starting in the summer of 1942 the TRE development team began experimenting with systems to project the display onto the windscreen, and by October had combined this with an image of the existing GGS Mk. II gyro gunsight to produce a true head-up display known as the "Automatic Pilot's Indicator", or API. A single example was fitted to