During the First World War, the tanks used in some marginal operations did not give satisfactory results. Hence, many western military chiefs (with exception of General De Gaulle, who almost prophetically had recognized its importance) had underestimated the usefulness of this new war instrument. But the German did not think like that. The Reichswehr, the German Army still attached to the Versalles Treaty, and still within the narrow limits set by that treaty, had manifested a huge interest for tanks, lucidly glimpsing their great possibilities. Not being allowed to build true tanks, the German used in their maneuvers false tanks formed by automobiles "armored" with fabric or paperboard, or also plasterboard imitations moved by two soldiers like clowns do with a horse disguise in the circus. It can also be said that, stimulated by the prohibition of building true tanks, the German military minds approached the work with greater determination to devise them larger and more powerful. Recalling the memories from the grim massacres which during the war of 1914-1918 had bleed out the infantry and dishonoured the military art, the clever minds of the Reichswehr saw in the functional utilization of tanks a new and more effective way of making war. It was precisely in those years when the German, eager for "revenge", started to study a future line of war by using large groups of tanks (armored divisions) able to operate at maximum speed without having to wait the slow and laborious advance of the infantry. Until that moment, for many generals formed in the battlefields of the preceding war, the infantry continued being the main weapon at whose service all the others should be used. Tanks, therefore, should be "at the service" of infantrymen. Its main objective was to accompany them, to open a way for them and to protect them from the enemy. But the German inverted the situation. They, or better said, some of them (because the old generals showed great perplexity) discovered a revolutionary weapon in the tank. The advocates of the primacy of tanks affirmed that in the future wars the enemy territory should not be conquered meter after meter at the pace of infantry, but through the fast irruption of armored units which, after penetrating deeply inside, would form "pockets" in which the enemy forces would be at the mercy of the infantry. Nowadays this concept could seem indisputable, but back then it raised a lot of controversies. The mere idea of reducing the infantry (the "queen of the battles") to the limited role of a later intervention to regroup the prisoners was considered to be absurd. Excellent minds of the German Army, such as Beck and Halder, opposed this idea with all of their energies. And Hitler, whose military "genius" has been many times questioned, that time took the right decision and warmly supported the thesis from General Guderian and others who at all costs supported the necessity of an extremely mobile army. When the campaign of Poland started, the German Army had six armored divisions. Half of the 288 tanks which constituted a division were PzKpfw (Panzerkampfwagen) I, also known as "sardine cans" because of their weak armor (they weighed six tonnes) and armament of two machine guns. Later came the PzKpfw II (nine tonnes and one 20-millimeter cannon), the PzKpfw III (15 tonnes and one 37-millimeter cannon) and the PzKpfw IV (20 tonnes and one 75-millimeter cannon). But for imposing the PzKpfw IV, in a quantity of 24 in some divisions, it was required all of the authority from Hitler, because the generals of the High Staff considered it to be too heavy. But these Panzerdivisionen would be those which revolutionized the art of war, allowing Hitler to conquer Europe. The truth is that they did not deserve so much. In fact, the success achieved led to exaggeratedly overrate their strength, and this is still nowadays a widespread conviction. It was not so much the (very relative) power of the Panzerdivisionen which revolutionized the way of making war, but their intelligent and functional utilization. If Hitler had used his tanks as a support for the infantry according to the former custom (and as the other armies continued doing) neither the Blitzkrieg nor the sound German successes would have existed.

The Pzkpfw (Panzerkampfwagen or Armored Combat Vehicle) Mark III, whose design dated back to 1935, entered operational service in time for taking part in the campaign of Poland, albeit in an almost experimental way, with the Panzer Lehr Bataillon. Due to practical reasons and for a quick construction, the tank was built in four parts constituted by welded plates: hull, turret and fore and rear superstructures, which were later riveted to each other. The Pzkpfw III practically constituted the backbone of the Panzerwaffe, operating with success in every front until the apparition of the Soviet T-34, of clearly superior performance. From that moment it was disappearing little by little, replaced by more modern and powerful tanks, but its hull continued being used until the end of the conflict for the manufacture of self-propelled artillery pieces of caliber 75 and 100 millimeters. Among its various versions there were some fitted with additional armor plates called "skirts", kept at a certain distance from the hull by means of a framework. They served for diminishing the effect of impacts from artillery and especially from the fearsome shaped charges. It was manufactured also a Flammpanzer (Flamethrower Tank) which instead of a cannon carried a thick flamethrower with 1000 liters of fuel.