As early as 1934/35, General Heinz Guderian envisioned two basic types to act as the most numerous equipment for the future German Panzer Divisions. The first vehicle was to be armed with anti-tank gun and two machine guns and second one was to be a support vehicle armed with a larger caliber gun. The first one eventually became known as Panzerkampfwagen III, which was to be a standard tank for the three light companies of a tank battalion. The second one became known as Panzerkampfwagen IV.
In 1935, development orders for a 15-ton full-tracked vehicle based on the specifications by Waffenamt were issued to MAN (Nurnberg), Daimler-Benz AG (Berlin-Marienfelde), Rheinmetall-Borsig (Berlin) and Krupp AG (Essen). In order to maintain secrecy, new vehicle was known as Zugfuhrerwagen (ZW) – platoon commander’s vehicle. The vehicle was designated Versuchkraftfahrzeug 619, Mittlerer Traktor (Medium Tractor) and 3.7 cm Geschutz-Panzerwagen.
Panzerkampfwagen III’s development began with a conflict between Waffenamt (the Ordnance Department) and the Inspector for Mechanized Troops about the main armament. Waffenamt selected and was satisfied with 37 mm gun, while the Inspector for Mechanized Troops demanded 50 mm gun. In the end, 37 mm gun was chosen as the main armament of the new vehicle. The decision was based on the fact that the infantry was already equipped with standard 37 mm Pak 35/36 L/45 anti-tank gun as well as that only one gun and one type of ammunition had to be produced. The turret and turret ring were still capable of mounting heavier gun as it was selected by the Inspector for Mechanized Troops. Armor protection was to be heavier in the front rather than rear since, new vehicle was to be used in forward elements of assault tank formations. The top speed was specified to be 40 km/h. The vehicle was to be operated by the crew of five men, with commander, gunner and loader in the turret and the driver and radio operator in the hull front. The communication between crewmembers was through the use of intercom system. Panzer III was the first of German Panzers to be equipped with intercom system for in-tank communications. Later on all of Panzers were equipped with this device which, proved to be very effective during combat.
Krupp’s MKA Prototype Trials and tests of new prototypes took place from 1936 to 1937 on testing grounds in Kummersdorf and Ulm. They resulted in Daimler-Benz design being chosen for full-scale production and in early 1937, Waffenamt ordered Daimler-Benz to produce first series (0-Series) of their design.
Krupp’s ZW prototype designated as MKA featured leafsprings and bogie wheel mountings type of a suspension. In turn, many features of this vehicle were used in the design of Panzerkampfwagen IV, which was designed by Krupp.
PzKpfw III design was composed of four sections – hull, turret, and front superstructure with the opening for the turret and rear superstructure with the engine deck. Each section was of a welded construction and all four were bolted together. The hull was divided into two main compartments divided by a bulkhead. The front compartment housed the gearbox and steering mechanism and the rear one both the fighting and engine compartment. Basic hull, turret, superstructure and crew layout remained unchanged throughout the production life of Panzerkampfwagen III series.
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In March of 1941, last Sd.Kfz.141 and first Sd.Kfz.141/1
Panzerkampfwagen III tank – Ausf J (8-serie) entered production. It was produced by Daimler-Benz, MAN, Alkett, Henschel, Wegmann, MNH and MIAG until July of 1942 with 2616 produced (chassis numbers 68001-69100 and 72001-74100). Ausf J had its armor protection significantly improved as it ranged from 10mm to 50mm. Increase in armor was accompanied by installation of new driver’s visor (Fahrersehklappe 50) and ballmount (Kugelblende 50) for a 7.92 mm MG 34 machine gun in the hull. New type of front access hatches was installed along with new air intakes on the hull front. From April of 1942, 20 mm spaced armor was added to the gun mantlet and/or superstructure front. 1549 vehicles produced from March of 1941 to July of 1942 were armed with 50 mm KwK 38 L/42 gun and two MG 34 machine guns. Those vehicles were designated as PzKpfw III Ausf J / Sd.Kfz.141. 1067 vehicles produced from December of 1941 to July of 1942, armed with 50 mm KwK 39 L/60 and two MG 34 machine guns. Those vehicles were designated as PzKpfw III Ausf J/Sd.Kfz.141/1. The only difference between both models was the main armament and ammunition stowage for 84 in contrast to previous 99 rounds. When encountered in North Africa, British nicknamed 50 mm L/60 Ausf J – „Mark III Special” The 50 mm L/60 gun was a significant improvement over the original 37 mm gun, although it was still inadequate to deal with American M4 Sherman and Soviet T-34/76 tank. In 1941/42, there was an unsuccessful attempt by Krupp to mount Ausf J with Panzerkampfwagen IV Ausf G’s turret to create new Panzerkampfwagen III variant designated Ausf K.
From August to November of 1942, 81 Ausf J tanks were produced as command tanks – Panzerbefehlswagen III mit 5cm KwK L/42 / Sd.Kfz.141. From March to September of 1943, additional 104 Ausf J were converted as well. The vehicle was basic Ausf J tank but lacked hull machine gun and carried less ammunition (75 rounds). It was fitted additional radio equipment and periscope.