At the end of the nineteenth century when he proposed his theory of evolution, Charles Darwin noted that there were many branches that led to unsuccessful species and hence to extinction. Of course, Darwin was talking about animals, but tanks, it would seem, followed broadly the same rules of evolution.
In the 20’s and 30’s, it was understood that tanks in the coming war would need to be able to deal with two major situations. The first were tank-versus-tank actions. Even the lightest tanks were capable of surviving explosions very close to the vehicle. Faced with the armour of a tank, explosive shell power alone was therefore of little value. To destroy a tank, it was obviously necessary to fire a projectile fast enough to penetrate the armour of the hull and disable the machine, or kill the men inside. Elementary physics tells us that force equals mass times velocity. For the job of destroying other tanks, the tank needs to be able to fire the heaviest practicable shell, at huge speeds. This produces enough force to punch through the armour of an enemy tank. Explosive power alone has little value against the thick armour of a tank. What gives the missile its penetrating power is the enormous velocity which slices through the armour of enemy vehicles. Even today, armour piercing rounds still tend to be solid shot which rely upon a very high velocity, and the enormous pressures and heat created by a round impacting on armour, in order to burn its way or melt its way through the armour to fly around inside, either destroying equipment or killing or injuring the crew.
Tanks of the Panzerwaffe silhouetted against the skyline during the advance to Stalingrad in August 1942.
The armour of most tanks of 1939 and 1940 vintage could be penetrated by relatively small calibre anti-tank weapons, but the armour piercing weapons which fire these high velocity shells were only useful in combat against other tanks. A variety of high explosive anti-tank rounds were therefore developed, which were designed to first penetrate the armour of an enemy tank, then explode inside the vehicle. This fine balancing act was rarely achieved in practice, and it is debatable whether the small amount of explosive contained in the shells was much more effective than the massive kinetic impact of a high velocity round.
In addition to other tanks, tanks needed to be able to deal with infantry and field guns. In these cases they needed to be able to fire a high explosive round. Here, the speed of the shell was less important; what mattered was the weight of explosive packed into the warhead. In simple terms, the bigger the shell, the bigger the explosion. High explosive shells - generally speaking - had a hollow cone into which high explosives were inserted and which were designed to detonate and throw out a lethal stream of metal splinters, which were particularly effective against infantry out in the open. Of course, high explosives were also useful for destroying non-armoured targets such as lorries and jeeps.
The drive to achieve the combination of destructive power and a tank-killing capability produced two radically different alternatives. Some countries opted for a balanced tank force with some tanks developed for anti-tank duties and others for high explosive capability.
This was certainly the case with the Wehrmacht: the Germans developed two separate types of tank, each specialised for a particular job. The first were the tank killers equipped with a high velocity anti-tank gun with a longer barrel of smaller calibre.
Most of the Panzer IIIs of 1939 vintage were equipped with the 37mm gun, designed to deal with enemy tanks. By contrast all of the heavier Panzer IV tanks were designed as infantry support tanks. They were equipped with a short barrelled 75mm gun, of lower velocity but higher calibre, ideal for firing high explosives.
As the short-barrelled 75mm gun was designed to fire high explosive in the close support role, the Panzer IV had to be made with heavier armour as this tank was designed to stay close to the infantry, and use the gun to deal with the usual infantry opposition, in the form of machine gun positions, block houses and light artillery. Although it did have an anti-tank capability, the early war 75mm gun was not really to be judged as an anti-tank weapon. The Panzer IV was designed to deal with those targets that a high velocity anti-tank gun could not cope with.
Kliest’s Panzers advance along a railway line during the early stages of Operation Barbarossa. Operating in conjunction with Guderian’s forces, these tanks helped to produce some of the largest hauls of prisoners on the Eastern Front.
In contrast to the Germans, who developed two different types of tanks to do different jobs, one solution tried by the armies of Britain, France, America and Russia was to house two types of gun in the same tank. This produced the massive multi-turreted tanks like the French Char 2c, the Russian BT-35 and the American Lee-Grant tank.
The dual turret idea was a failure, an evolutionary blind alley which was cruelly exposed on the battlefield. The two turrets made the tank difficult to operate, it was impossible to co-ordinate the guns and the sheer size of the machines presented a huge target that was difficult to miss. With the figure of her commander perched some 15 feet above the ground, it was easy to see why the Lee-Grant tank could not be successfully hidden on the battlefield.
As the war progressed, the same course was ultimately adopted by all sides, which was to combine both an anti-tank capability and an infantry support role in one well armoured vehicle which mounted the largest possible calibre of main gun with the highest practicable velocity. The larger calibre effectively gave it a good high explosive firing capability and the high velocity gave it a deadly killing power against other tanks. The Panther tank of 1944 vintage was considered by many to be the ultimate combination of these two features.
Despite the undoubted promise of machines like the Panther, in 1945, when the war ended, Germany was still developing the super heavy Panzer VII, a huge metal monster, weighing over one hundred tons, massively armoured and sporting a huge 122mm main gun. In an untypically humorous moment, this machine, designed to lead the Nazi war machine, was nicknamed ‘Maus’ (Mouse). The Maus was never to see action and only four prototypes were built, but it seemed that the crazed minds of the Third Reich would never give up the quest to be the best and the biggest, whatever the cost, but as the humble T-34 had proved, in matters of evolution, sometimes quantity matters as much as quality.
A group of tank men take a well-earned rest from the pressures of life on the move. The strain of constant action can be seen etched into their faces.