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.