In the mid-1930s German authorities intensified their efforts to find a way around the post-war limitations imposed on the country by the Treaty of Versailles.
Hitler’s drive to modernize his armed forces gained a new momentum with the arrival on stage of Col. Heinz Guderian – the future spiritus movens of German armored warfare doctrine. Behind the scenes German design teams were busy working on prototypes of vehicles that would soon become the tools of the future war – light Pz.Kpfw. I and II, heavy (in keeping with contemporary classification) Pz.Kpfw. IV and medium Pz.Kpfw. III armed with a 37 mm gun. In the early stages of fighting in France it became clear that the vehicle didn’t carry enough punch and in later marks of the tank the 37 mm main gun was superseded by a 50 mm weapon. The ultimate version of the Pz.Kpfw. III was armed with a short barrel 75 mm gun, the largest that the tank’s turret could accommodate.
It was already in the mid-1920s that first efforts were made to equip German army with tanks. Early attempts to design and build a thoroughly modern armored vehicle can be traced to December 1933 when Krupp received a requirement from Heereswaffenamt (Army Ordnance Office) for a 10 ton tank armed with a 37 mm main gun and machine guns.
During a meeting held on January 11, 1934, where the future needs of armed forces were discussed, a decision was made to procure armored combat vehicles. As a result, two types of tanks were to be developed: the basic tank, initially designated Gefechtskraftwagen 3.7 cm (Vskfz. 619) armed with a 37 mm gun mounted in a rotating turret and an escort tank (Begleitwagen - B.W., manufactured as the Pz.Kpfw. IV) armed with a heavier caliber weapon. The former were later “camouflaged” as a Zugführerwagen – Z.W., or a platoon’s leader tank. In official documentation that vehicle can be found under several different designations:
– 3.7 cm Geschütz–Kampfwagen,
– 3.7 cm Geschütz–Panzerwagen (Vskfz. 619),
– 3.7 cm Geschütz–Panzerkampfwagen,
– 3.7 cm Panzerkampfwagen.
Before long, Waffenamt Prüfwesen 6 (department of the Army Ordnance Office responsible for development of armored and mechanized equipment) formulated key technical specifications of the future Z.W. tank. Weighing in at 10 tons, the vehicle was to be manned by a crew of five. A six-speed Zahnradfabrik Friedrichshafen SSG 75 transmission was to be coupled to a liquid-cooled Maybach HL 100 engine developing 300 hp to accelerate the tank to a speed of 40 km/h.
Work on the Z.W. medium tank began simultaneously at Friedrich Krupp plant in Essen, Rheinische Metallwaren und Maschinenfabrik AG in Berlin (after merger with August Borsig GmbH the company operated as Rheinmetall-Borsig AG), Maschinenfabrik-Augsburg-Nürnberg AG (MAN) in Augsburg-Nuremberg and Daimler-Benz AG in Berlin. The last three were involved in the design of the chassis, with the task to build a prototype eventually going to MAN and Daimler-Benz. Rheinmetall (whose chassis didn’t make the grade) and Krupp (didn’t participate in the chassis design) were in turn given contracts to develop the new tank’s turret. In addition, Daimler-Benz was directed to develop a chassis with an alternative configuration of the running gear, designated as Z.W. 3 and Z.W. 4.
By August 1934 Krupp had delivered two test turrets (Turm 1 and Turm 2). Following live fire tests carried out on August 20, 1935 in Meppen, some modifications were recommended before the turrets could be cleared for a full-scale production. The following August Daimler-Benz delivered their chassis prototype designated Z.W. 1, while MAN most likely didn’t complete the assigned task. In late 1935 turrets designed and built at Rheinmetall and Krupp were mated to the Z.W. 1 chassis, before the vehicles were sent for tests. During field tests the prototype equipped with Krupp’s turret performed better and was subsequently selected for a full-scale production.
Versions armed with a 37 mm gun
Daimler-Benz received an order for ten Pz.Kpfw. III vehicles in December 1935 and by the end of 1937 all ten examples had rolled off the assembly lines. The vehicles received chassis numbers 60101 to 60110, official designation Pz.Kpfw. III (3.7 cm) Ausführung A (factory designation 1 Serie/Z.W.) and ordnance inventory number 141 (Sonderkraftfahrzeug 141, or Sd.Kfz. 141).
The tank’s running gear consisted of a pair of drive wheels, two idler wheels, two pairs of return rollers and five pairs of cast steel, rubber-rimmed double road wheels supported by steel arms and coil spring suspension.
The tank was powered by a liquid-cooled Maybach HL 108 TR developing 250 hp at 2,800 rpm. It was coupled to a manual Zahnradfabrik ZF SFG 75 transmission with five forward gears plus reverse. The vehicle’s average speed was 22 km/h, or 10 – 12 km/h in off-road conditions. Pz.Kpfw. III Ausf. A featured rolled steel armored protection measuring from 5 to 14.5 mm in thickness. The turret’s armor was from 10 to 16 mm thick. The tank’s main armament was a 3.7 cm KwK L/46, 5 gun. Two MG 34 7.92 mm machine guns were mounted to the right of the main gun.
Later in 1937 a new version of the tank was developed - Pz.Kpfw. III (3.7 cm) Ausf. B (2 Serie/Z.W.), which was an improved variant of the Z.W. 3 prototype. In total, between November and December, Deimler-Benz delivered 15 vehicles (chassis numbers 60201 to 60215). The new version of the tank featured a completely redesigned running gear. Five large road wheels were replaced with eight smaller ones, which were arranged into four two-wheel bogies. Each side of the tank featured two leaf-spring blocks, which provided suspension for two pairs of bogies. In addition, each pair of bogies was equipped with a shock absorber. The tank also featured three pairs of return rollers, instead of two in the previous version.
Another short-series iteration of the tank was Pz.Kpfw. III (3.7 cm) Ausf. C (Sd.Kfz. 141) (3a Serie/Z.W.), which was developed using the Z.W. 4 prototype. Tanks in this configuration were built between June 1937 and January 1938 by Deimler-Benz. Turrets were delivered by Krupp and Alkett (Altmärkisches Kettenwerk GmbH) in Spandau and Falkense. Similarly to the “B” model, 15 examples of that version were manufactured (chassis numbers 60301 – 60315). There were only minor modifications to the tank’s suspension design. A 2-4-2 arrangement was introduced with the first and last bogies braced under small spring-leaf assemblies mounted parallel to the ground, while the two middle bogies were mounted on similar, but much larger leaf-spring blocks. In addition, the front and rear bogies featured their own half-elliptical shock absorbers mounted over the first and eighth road wheel.
Pz.Kpfw. III Ausf. C was superseded on assembly lines by the next version designated Pz.Kpfw. III (3.7 cm) Ausf. D (Sd.Kfz. 141) (3b Serie/Z.W.), whose production began in January 1938 at Daimler-Benz plant. Turrets were delivered by Krupp and Alkett. A total of 30 examples of the “D” model were delivered in two production runs. The main batch of 25 vehicles (chassis numbers 60316 – 60340) was ready in September. The remaining five examples (60221 – 60225) received turrets and hulls from Ausf. B tanks that had been previously converted into StuG III assault guns.
The vehicle’s running gear was largely identical to previous versions, with the exception of redesigned mounting of shock absorbers over the second and fifth road wheel and a new design of return rollers and idlers. The short spring-leaf blocks mentioned above were now mounted at an angle, rather than parallel to the ground, as was the case in the previous version of the tank. The vehicle was also equipped with a synchronized Zahnradfabrik ZF SSG 76 seven-speed transmission (six forward gears and reverse).
All four versions of the tank described above were in fact test vehicles, with each successive iteration being an improved version of the previous model. A full-scale production of the tank wasn’t launched in earnest until the Pz.Kpfw. III (3.7 cm) Ausf. E (Sd.Kfz. 141) (4 Serie/Z.W.) variant was ready in December 1938. The new version featured a much improved running gear developed by Heinrich Ernst Kniepkamp, which was designed to allow the vehicle to achieve speeds of up to 70 km/h (40 km/h was still recommended as top speed, since faster travel caused blistering and separation of rubber tires on the tank’s road wheels). The new arrangement of the drive gear proved to be such a success that it was used in all subsequent marks of the vehicle. Its main features included the use of six pairs of road wheels mounted on torsion bars. Lighter idlers were also introduced, but the arrangement of three sets of return rollers remained unchanged. Both road wheels and return rollers featured solid rubber tires.
In addition to Daimler-Benz, the new tank was also manufactured by MAN. By October 1939 96 vehicles had been assembled – 41 manufactured by Daimler-Benz (60401 – 60441) and 55 by MAN (60442 – 60496). Turrets were supplied by Krupp (six examples) and Alkett (90 units).
Front and sides of the vehicle were made of 30 mm armor, rear was 20 mm thick, bottom – 16 mm, while the top of the hull was 25 mm thick. The machine gun was installed in a new mount (Kugelblende 30) to allow for the increased thickness of the armor. The tank’s turret also saw some modifications with its armor protection thickness increased as follows: front, sides and gun mantlet – 30 mm, top – 10 mm, cupola – 30 mm. Additional armor caused the overall weight of the vehicle to reach 19.5 tons. To compensate for that a more powerful, 12-cylinder Maybach HL 120 TR engine was installed, which delivered 285 hp at 2,800 rpm. The tank also received a new Variorex SRG-328-145 transmission featuring 10 forward gears and reverse.
The next iteration of the tank, Pz.Kpfw. III (3.7 cm) Ausf. F (Sd.Kfz. 141) (5 Serie/Z.W.), was manufactured in parallel with production of the “E” model, but in much greater numbers. Its production was launched in August 1939 and continued until April/May 1941 at which point 435 vehicles had been assembled. The “F” variants were manufactured in several locations: Alkett – 36 examples (61601 – 61636), Daimler-Benz – 95 vehicles (61101 – 61195), MAN – 96 tanks (61001 -61096), Fahrzeug- und Motorenbau GmbH (FAMO) in Breslau (Wroclaw) – 28 machines (61201 – 61228), Henschel & Sohn in Mittelfeld-Kassel – 120 examples (61301 – 61420) and Mühlenbau und Industrie AG (MIAG) in Braunschweig – 60 tanks (61501 – 61560).
Some of the turrets were delivered by Wegmann plant in Kassel. In most respects that variant was identical to the previous version. There were some minor differences, including an additional air scoop into the engine compartment and the use of a different Maybach engine (HL 120 TRM), albeit still rated at 285 hp.
The first batch of 335 tanks, which had been produced by July 1940, featured the 3.7 cm KwK L/46, 5 main gun and three MG 34 machine guns, while the last 100 examples received a 50 mm gun and a new designation – Pz.Kpfw. III (5 cm) Ausf. F.
Recommended - Armour
Versions armed with a 37 mm gun