Increased Protection on PzKw 3 and 4, WWII Tactical and Technical Trends, No. 25: May 20, 1943 (Lone Sentry)

The history of the changes in the light medium PzKw 3 and 4 demonstrates how fortunate the Germans were in having a basic tank design that could be improved as battle experience indicated, for a basic design can be improved and still remain familiar to the users. Furthermore, the problems of maintenance and supply of parts are greatly reduced--and these problems are a major factor in keeping tanks ready for operational use.

a. The PzKw 3

(1) General

The Germans seem to be making a gradual increase in thickness of armor-plate as the guns used against it increase in hitting power and range. The PzKw 3 medium tank is illustrative of this trend in tank armor and design, and affords a remarkable example of what can be done to improve the armor protection and fighting efficiency of a tank without changing its basic design. The key of this basic design is the welded main structure which allows heavier plates to be used when desired. Also, operating components of the tank are not hung on the plates, likely to be changed to thicker ones.

(2) Pre-War

The early model PzKw 3 (produced in 1936-38) had basic armor of .59-inch homogeneous plate. At this time there were only 5 bogie wheels on a side instead of the present 6. There is a gap in the formation until 1939, when the tank appeared with 1.18-inch face-hardened armor on the turret and front. This model had 6 bogie wheels on the side. The side armor which forms a great part of the chassis was of softer, machineable-quality plate, due both to necessities of manufacture and to the undesirable weakening effect on hardened plate of the necessary suspension and bracket holes. The model also had improved aperture protection in the form of an external moving mantlet, additional armor around the machine-gun port, and an improved double-flap driver's visor. It appears that these features were added with the modification of but 2 plates on the tank.

(3) 1941 Changes

In 1941, as more powerful guns were being used against tanks, 1.20 inches of additional armor plate was bolted against the plates on the front of the superstructure and on the upper and lower nose-plates. The 1.18-in. basic plates were face-hardened to a Brinell hardness of 600 to 800 and 1.20-in additional plates were the same. About a year later, in January 1942, the tank appeared with a basic armor of 1.96 inches on the front and back, the side-armor thickness remaining unchanged at 1.20 inches. This armor was face-hardened and performed well against monobloc shot, but once the face-hardening was pierced, the shell fragments penetrated the remainder with ease.

(4) 1942

Therefore, in June 1942, a .79-inch additional plate was bolted on the gun mantlet and front superstructure as a means to defeat a shot with a piercing cap. Between this plate and the basic armor was an air gap or space, varying from 4 to 8 inches. The plate conformed roughly to the shape of the section covered. The spaced armor seems to have been a field expedient, resulting undoubtedly from the demonstrated fact that the spare section of track carried on the front of German tanks gave additional protection. This method of adding armor was officially recognized, as later models had brackets fitted for installing spaced armor when desirable.

b. PzKw 4

(1) Early Models

The PzKw 4, a slightly heavier tank than the 3, has passed through much the same line of development. Little is known about the models A, B, and C of this tank, but Model D was in use during the greater part of the period 1940-43. Specimens of armor cut from Model D have been examined. Of these, only the front plate of the hull appears to be face-hardened; this plate is carburized. All of the plates were high-quality, chromium-molybdenum steel, apparently made by the electric-furnace process.

The first increase in the armor of this tank was reported in 1941, when it was observed that additional plates had been bolted over the basic front and side armor. The additional plates on the front were 1.18 inches thick, making a total of 2.36 inches, and those on the sides were .79 inches thick, making a total of 1.57 inches. In its early stages, this addition was probably only an improvised measure for increasing the armor protection of existing PzKw 4 models in which the thickest armor was only 1.18 inches.

(2) Model E

In Model E, which had 1.96 inches of single-thickness nose plate, the fitting of additional armor on the front of the superstructure and on the sides of the fighting compartment was continued. Although the arrangement of the additional side armor on this model appears to have been standardized, that on the front superstructure was by no means uniform.

Three PzKw 4 tanks have recently been examined. In each case, extra armor had been fitted to the vertical front plate carrying the hull machine gun and driver's visor. It had also been added to the sides of the fighting compartment both above and below the track level. The extra protection above the track level extended from the front vertical plate to the end of the engine-compartment bulkhead. It was thus 110 inches long and 15 inches deep. The pieces below the track level were shaped in such a way as to clear the suspension brackets. They were 90 inches long and 30 inches deep. All this extra side protection was .97 inch in thickness.

The vertical front plate was reinforced in three different ways. On one tank, two plates were used; one over the plate carrying the hull machine gun, this additional plate being cut away to suit the gun mounting, and the other plate over the driver's front plate, cut to shape to clear his visor. On the second tank, the arrangement around the hull gun was the same, but the extra protection around the driver's visor consisted of two rectangular plates, one on each side of the visor, there being no extra plate immediately above the visor. On the third tank, the only additional front armor was the plate around the hull machine gun. No additions had been made to the driver's front plate. In all cases, the extra frontal plating was 1.18 inches thick; the nose plate was unreinforced, but it was 1.97 inches thick, and the glacis plate was .97 inch thick. The final drive casings of PzKw 4 tanks of this period were also sometimes reinforced by .79-inch protecting rings. The additional plates on the front were face-hardened.

It is probable that the reinforced armor on the front superstructure of this model will compare closely with that on the corresponding parts of the PzKw 3 of 1941 and that the 1.96-inch nose plates will not differ substantially from those on the more recent PzKw 3's of June 1942, known as "Model J."

The reinforced (.79 inch plus .79 inch) side armor has, however, no counterpart in any PzKw 3 model. The additional plates are of homogeneous quality and have a Brinell hardness of about 370 on the front surface.

(3) Model F

Towards the end of 1941 the Germans introduced a PzKw 4, Model F, having 1.96-inch frontal armor (gun mantlet, front superstructure and hull nose-plates) and 1.18-inch side armor. In this and many other respects, the Model F conforms more closely than its predecessors to the corresponding model of the PzKw 3 (in this case PzKw 3 Model J). So far, the armor of the PzKw 4 Model F has not been examined to ascertain its chemical and ballistic properties, but there is a strong probability that these do not differ greatly from those of the PzKw 3, Model J.

(4) Model G

This model which mounts the long 75-mm gun, Kw.K 40, was first encountered in June 1942. It is reported from the Middle East that its armor is the same as that of Model F; namely 1.96 inches on the front, and 30 mm (1.18 inches) on the sides.