After the Battle of Stalingrad, in September 1942 the Wehrmacht's arms bureau, the Waffenamt, called for a new standard for assault weapons: 100 mm of armor to the front, 40–50 mm on the sides, wider tracks, ground clearance of 50 cm, top speed of 26 km/h and the lowest possible firing positions. The new Panzerjäger ("tank hunter") design would be armed with the same 7.5 cm gun as fitted to the Panther: the Pak 42 L/70. Initially a new chassis was planned, but that of the Panzer IV had to be used.
Combat experience gained during the 1942 campaigns indicated to German staff planners that the existing Sturmgeschütz close support artillery vehicles would have to be up-gunned if they were to continue to be used as tank destroyers, and the future standard weapon was selected as the long version of the 7.5-cm (2.95-in) tank gun fitted to the Panther tank. This gun was 70 calibres long (as opposed to the 49-calibre length of the tank and antitank versions of the Pak 40 family) and to house this gun in vehicles such as the Sturmgeschütz III would require considerable modifications. These modifications would take time so it was decided to adapt the larger PzKpfw IV tank chassis to act as a 'fail safe' model. Design work was soon under way on this new model, which emerged in 1943 as the Jagdpanzer IV Ausf F für 7.5-cm Pak 39 or Panzerjäger 39, but by the time the first examples were ready the long 7.5-cm guns were earmarked for the Panther tanks and so the first examples had to be content with 48-calibre guns.
Previous efforts to mount bigger guns on smaller chassis resulted in the Marder series as well as StuG IIIs. The Marder series were tall and had open crew compartments. The new design had a low silhouette and completely enclosed, casemate fighting compartment.
The Jagdpanzer IV used Panzer IV chassis 7 (known as BW7), but the almost-vertical front hull plate was replaced by sloped armor plates. Internally, the layout was changed to accommodate the new superstructure, moving the fuel tanks and ammunition racks[clarification needed]. Since the Jagdpanzer lacked a turret, the engine which originally powered the Panzer IV's turret could be eliminated.
The new superstructure had 80 mm thick sloped armour, which gives a much greater armor protection than a vertical armor of 100 mm. To make the manufacturing process as simple as possible, the superstructure was made out of large, interlocking plates which were welded together.
Armament consisted of a 7.5 cm main gun, originally intended to be the Pak 42 L/70, but due to shortages older guns were initially used, the 7.5 cm Pak 39 L/43 for pre-production, and the 7.5 cm Pak 39 L/48 for initial production variant. These were shorter and less powerful than the Pak 42.
Installing the much heavier Pak 42 meant that the Jagdpanzer IV was nose heavy, especially with the heavy frontal armor. This made them less mobile and more difficult to operate in rough terrain, leading their crews to nickname them Guderian-Ente ("Guderian's duck"). To prevent the rubber rims of the roadwheels being dislocated by the weight of the vehicle, some later versions had steel roadwheels installed on the front.
The final prototype of the Jagdpanzer IV was presented in December 1943 and production started in January 1944, with the Pak 39 L/48 armed variant staying in production until November. Production of the Pak 42 L/70 armed variants started in August and continued until March/April 1945.
On 19-22 August 1943, after the Battle of Kursk, Hitler received reports that StuG IIIs performed better than Panzer IV within certain restraints of how they were deployed. It was thus intended to stop production of the Panzer IV itself at the end of 1944 to concentrate solely on production of the Jagdpanzer IV, but the Panzer IV was in production all the way until the end of the conflict along with Jagdpanzer IV.
The first of these Jagdpanzer IVs appeared in October 1943. They consisted of the well-tried suspension and engine layout of the PzKpfw IV allied to a new armoured carapace with well sloped sides. This hull was much lower than the hull/turret combination of the tank, and mounted the gun in a well protected mantlet on the front hull. The result was well-liked by the Panzerjäger crews, who appreciated the low silhouette and the well-protected hull, so the Jagdpanzer IV was soon in great demand. The gun was powerful enough to tackle virtually any enemy tank, and in action the Jagdpanzer IV was soon knocking up appreciable 'kill' totals, especially on the Eastern Front where most were sent. The secondary armament of two 7.92-mm (0.312-m) MG34 or MG42 machine guns also proved highly effective.
Jagdpanzer IV muzzle brakes were removed even from the earliest vehicles. This was to reduce dust kicked up by gun firing, which would give away the vehicles position. Muzzle brakes also send sound waves in all directions. This makes for an apparently louder report. Not so good, if you are trying to ambush armor. A gun without a brake will send its sound waves, basically, in the direction of the projectile. Also, the brake will tend to have an effect on the accuracy of the gun.
Many Panzer commanders considered that the Jagdpanzer IV was good enough in its original form to require no up-gunning but Hitler insisted that the change to the long gun had to be made.
Guderian believed the StuG III to be sufficient as a self-propelled gun, and felt production should have been focused on tanks. Because of its nose-heavy characteristics and General Guderian’s view that the Jagdpanzers were unnecessary, the crews christened the Panzer IV lang variants Guderian’s Ente, meaning Guderian’s Duck.
Thus during 1944 some Jagdpanzer IV mit 7.5-cm Stuk 42 equipments with the longer L/70 gun appeared, but the changeover on the production line took time, too much time for Hitler, who insisted that the changeover to the new gun had to be made even if it meant diverting all PzKpfw IV tank production to that end. Thus a third Jagdpanzer IV appeared, this time a hasty conversion of a basic PzKpfw IV hull to take a form of Jagdpanzer IV sloping carapace and mounting the 70-calibre gun.
This conversion was known as the Panzer IV/70 Zwischenlösung (interim) and was in production by late 1944. In service the 70-calibre gun Jagdpanzer IVs proved to be powerful tank killers, but the extra weight of the long gun made the vehicles nose-heavy to the extent that the front road wheels had to be ringed with steel instead of rubber to deal with the extra weight, The gun weight also reduced the overall performance of the vehicle, especially across rough terrain. But by late 1944 and early 1945 such drawbacks simply had to be overlooked, for the Allies were at the gates of the Reich and anything that could be put into the field was used. The Jagdpanzer IV proved to be a sound Panzerjäger that enabled the Germans to utilize existing production capacity and maintain the PzKpfw IV line in being when it would otherwise have been phased out. In service the Jagdpanzer IV was a popular vehicle and a powerful tank-killer.
Specification
Jagdpanzer IV mit 7.5-cm Stuk 42
Crew: 4
Weight: 25800 kg (56,879 lb)
Powerplant: one Maybach HL 120 petrol engine developing 197.6 kW (265 hp)
Dimensions: length overall 8.58m (28 ft 1.8 in); width 2.93 m (9 ft 7.4 in); height overall 1.96 m (6 ft 5.2 in)
Performance: maximum road speed 35 km/h (22 mph); road range 214 km (133 miles); gradient 57 per cent; vertical obstacle 0.6 m (23.6 in); trench 2.3 m (7 ft 6,6 in); fording 1.2 m (3 ft 11 in)
