Polish armoured forces on the brink of war
It was already clear during WWI that wars of the 20th century will be "wars of the motor", both in the air and on the ground. However, this did not mean that all nations hurried to fill their arsenals with aeroplanes and tanks. Losing nations were prohibited from having them by peace treaties. The victorious nations, especially Britain and France, had the opposite problem: what to do with the enormous number of fighting machines unnecessary in peace time? The masses of British "rhombuses" and French Renault FTs had three options: scrap, conservation, or export. It's not surprising that many nations' armoured forces came into being with these vehicles.
This was the case with Poland's army. As a part of arms shipments during the Soviet-Polish war, Poland received tanks from the Entente nations. Later, the Poles bought and built new types of tanks, but by the start of WWII Poland still retained several dozen Renault FTs, ancestors of the classical tank layout.
The desire to have a numerous tank force was limited by industrial and economical abilities of the country. Desire and ability were balanced with a compromise: by 1939 the core of the Polish armoured forces consisted of inexpensive TK-3 and TKS tankettes.
At the same time, Poland was aware of what was happening in neighbouring countries. The fact that Germany, Czechoslovakia, and the USSR placed their resources into "proper" tanks, mostly armed with cannons, forced Poland into an arms race. The purchase of French Renault R 35 and British "best-seller" Vickers Mk.E tanks resulted in the domestically produced 7TP tank based on the British prototype.
During peacetime, the Polish armoured forces included:
- 10 armoured battalions
- The 11th experimental tank battalion at the Modlin training center
- 10th motorized cavalry brigade
- Two groups of armoured trains
Pre-war armoured battalions were large units with a complicated structure and varied armament. Soon before the fighting started in 1939, the Poles restructured their armoured forces in addition to other preparations for mobilization. By the start of the war, Poland had the following to put up against the Wehrmacht's 7 tank divisions and 4 light divisions:
- 2 light tank battalions equipped with 7TP tanks (49 tanks each)
- 1 light tank battalion equipped with R 35 tanks (45 tanks)
- 3 independent light tank companies (15 Renault FT each)
- 11 armoured battalions (8 armoured cars and 13 TK-3 or TKS tankettes each)
- 15 independent reconnaissance companies (13 TK-3 or TKS tankettes each)
- 10 armoured trains
In addition, the two motorized brigades (10th cavalry brigade and Warsaw armoured motorized brigade) had a company each of 16 imported Vickers Mk.E tanks and two companies of tankettes.
Considering the fact that Poland had no medium tanks and that the armament of the 7TP was superior to that of the German PzI and PzII, one can say with some confidence that the light 7TP could act as a medium tank among the numerous tankettes.
6-ton Vickers and the armour scandal
The Polish ministry of defense kept ties with the Vickers-Armstrong company since 1926. The British demonstrated several of their vehicles (Mk.C and Mk.D), but the Poles didn't like them. Things got moving once they saw the Mk.E (Vickers 6-ton), which was destined to become one of the most important steps in tank history. Polish representatives began familiarizing themselves with the tank even before it was finished in 1928. A prospective chassis was shown to their delegation in January of 1927 and the military made the decision to buy 30 of this not yet existing tank in August of 1927.
The steep price of the new tank forced Poland to consider the French Renault NC-27 tanks, an attempt to breathe life into the rapidly ageing Renault FT. The attempt to be thrifty ended poorly. The 10 tanks bought in France made such a poor impression that it was decided to go back to Vickers. Another alternative that interested the Poles was the convertible drive Christie tank, but the American engineer did not manage to deliver a sample to Poland in time.
The Vickers Mk.E was available in two modifications: the single turreted Type B with a cannon and a machinegun and the two-turreted Type A with two machineguns. After trials of a sample in September of 1930, Poland made the decision to purchase 38 (some sources say 50) two-turreted tanks along with a license to produce them.
The new purchase was not without flaws. Even during preliminary trials in 1930 it turned out that the weakest link of the tank was the 90 hp air cooled Armstrong-Siddeley gasoline engine. The cruising speed of the tank with this engine was 22-25 kph, but at the maximum speed of 37 kph it would overheat within 10 minutes.
The second problem, a no less important one, was the quality of the armour, known in Poland as the "armour scandal". When the tanks arrived, it turned out that their armour was of lower quality than advertised. The 13 mm front armour was penetrated at a range of 350 meters by a 12.7 mm machinegun. The scandal was settled by lowering the cost of the shipment down to 3165 pounds sterling per tank from 3800.
16 Vickers tanks had a 13.2 mm machinegun installed into one turret, and another 6 received a 37 mm gun. Later, 22 of the British bought tanks were rebuilt into single-turreted versions with short 47 mm guns and coaxial machineguns.
T-26's Polish twin
After the Soviet-Polish war, the USSR seriously expected that Poland retained plans of aggression against its eastern neighbour. Fearing Poland's ability to achieve superiority in tanks (fearing in vain, as Poland was unable to produce more than 150 real tanks), the USSR carefully observed the development of Poland's armed forces. Perhaps this was one of the reasons for the simultaneous interest of the USSR in the Vickers and Christie tanks (at least, this is the theory proposed in Polish sources). As a result, Christie became the progenitor of thousands of BT tanks (and the experimental Polish 10TP) and Vickers of a thousand T-26es and 134 7TPs.
As mentioned above, Poland bought a license to produce the tanks along with a British-made batch. However the license did not include the engine, and the air cooled gasoline engine was unsuitable for a tank anyway. The Swiss 110 hp Saurer diesel engine was chosen as a replacement, as it was already produced in Poland under license. This rather arbitrary choice (the Saurer was the only engine of sufficient power and size produced in Poland), the 7TP became the first European tank to use a diesel engine, and among the first in the whole world.
The use of diesel engines became widespread in tank design over time. Its advantages include fuel that is harder to ignite, better torque, and lower fuel consumption, which increased range. However, the engine had one drawback: its dimensions and bulky radiators required making the engine compartment taller, resulting in a hump that became the most obvious distinction of the Polish tank from the Vickers Mk.E or the T-26.
Cutaway of the Vickers 6-ton (above) and the 7TP (below).
The Poles also fought against the other drawback, the poor armour, but their solution was only a half-measure. Instead of 13 mm of homogeneous armour, their tanks used 17 mm of surface hardened armour. The driver's hatch was only 10 mm thick, the sides were 17 mm thick in the front and 9 mm in the rear. The rear part of the hull was 9 mm thick (6 mm in early models), and the early models had grilles for air intake in the rear as well. The dual turrets had 13 mm of armour all around. Naturally, this tank was still vulnerable to cannon shells.
The new tank, initially called VAU 33 (Vickers-Armstrong-Ursus, or in some sources, Vickers-Armstrong Ulepszony) received a reinforced suspension and a new transmission. The tank was equipped with a four-speed gearbox (plus one reverse). Its mass grew to 7 tons, which was the cause of the name change to 7TP (7 ton Polish tank, analogous to the "6-ton Vickers").
Two prototypes of the two-turreted 7TP named Smok (Dragon) and Słoń (Elephant) were built in 1934-35. Both were built from mild steel and used components bought from Vickers.
Second 7TP prototype used as an armoured draisine.
The first batch of two-turret 7TP with machinegun armament was ordered in March of 1935. They were armed with turrets left over from Vickers tanks that were converted to the single turret variant. This was a temporary measure, as the military had not yet finalized its decision regarding the final gun and turret design. The 47 mm Vickers gun was rejected singe it had poor penetration. The British proposed a new hexagonal turret with a more powerful 47 mm gun, but the Poles rejected that proposal as well in favour of the Bofors design based on the L-30 and L-10 tank turrets. This was not surprising, since the 37 mm Bofors gun was already used by the Polish army as a towed anti-tank gun.
7TP prototype with a Bofors turret
The Swedish two-man turret was altered in Poland. It received a bay in the rear for a radio and additional ammunition as well as Polish optics, including the Gundlach periscope. The patent for that periscope was sold to Vickers, and would later become a standard for Allied tanks. A 7.92 mm water cooled machinegun was installed as secondary armament (the two-turret design was armed with two of these machineguns). From 1938, Polish N2/C radios were installed in battalion, company, and platoon commanders' tanks. 38 of these radios were made, but not all were installed. The armour of the 7TP single turret was 15 mm thick all around and 8-10 mm thick on the roof. The protective shroud around the machinegun was 18 mm thick in the front and 8 mm thick around the barrel.
Two radio-equipped 7TP tanks on parade in Těšín, October 2nd, 1938.
The single turret 7TP weighed 9.9 tons, the two turret 7TP weighed 9.4 tons. The maximum speed of the tank was 32 kph, the operational range was up to 150 km on roads and 130 km off-road (Soviet sources say 195 and 130 km respectively). Both variants of the 7TP had a 3 man crew. The tank carried 80 shells for its 37 mm gun.
Despite the differences in the details regarding batch sizes and precise dates, sources agree on the number of tanks built. Including two prototypes, 134 tanks of this type were made. The ministry of defense budget allowed it to purchase a company of tanks per year. After the first batch of 22 tanks in 1935, 16 tanks were built in 1936. 18 7TPs were ordered in 1937. This snail's pace was unacceptable, and the sale of four companies of obsolete French Renault FTs to the Spanish Republicans (recorded as a sale to China and Uruguay) made it possible to order 49 new tanks in 1937. However, the military's tastes were bound by the manufacturing capacity of the factories, where both the 7TP tank and the C7P tractor competed for the assembly line. As a result, more tractors than tanks were built before the war began, about 150.
In total, 132 production tanks were built (the last 11 entered the military in September of 1939), 108 with a single turret and 24 with two turrets (alternative numbers: 110 and 22).
C7P Artillery Tractor made with 7TP components and assemblies.
Amount of tanks ordered:
22 (produced by summer of 1936)
16 (produced by spring of 1937, some without armament)
18 (produced by summer of 1938)
49 (produced by May of 1939)
16 (produced by summer of 1939)
16 (only 11 were completed by the end of September)
Even though Sweden, Bulgaria, Turkey, Estonia, the Netherlands, Yugoslavia, Greece, and possibly Republican Spain expressed interest in buying these tanks, limited industrial capacity and priority given to tanks for domestic use meant that the 7TP was not exported.
Combat use and comparison
Two companies of 7TP tanks (32 tanks in total) were included in the Silesia operational group and participated in the invasion of Těšín Silesia, a contested territory that was awarded to Czechoslovakia as a result of an international arbitrage in 1920. Czechoslovakia, which was simultaneously invaded by Germany as a result of the Munich Agreement, offered no resistance, so the participation of the 7TP in the conflict was largely psychological.
Polish 7TP tank from the 3rd Armoured Battalion (1st platoon) crossing Czechoslovakian anti-tank obstacles on the Czech-Polish border.
In September of 1939, Polish tanks were successfully used against the German forces. Their characteristics significantly surpassed those of the German PzI tanks (which was made clear during the face-off between the "turreted tankette" and the Soviet brother of the 7TP in Spain), somewhat surpassed the PzII, and was roughly equal to the LT vz. 35, LT vz. 38 and PzIII used by the Wehrmacht. Both light tank battalions that used 7TP tanks proved themselves against the Germans, but their small numbers meant that they could not meaningfully impact the course of the war.
German Pz35(t) knocked out by a 37 mm gun (either towed or tank). The white cross is covered in mud. German tankers tried to conceal this revealing marking which made an excellent target.
For example, on September 4th, two companies of the 2nd Polish Light Tank Battalion participated in the defense of the southern outskirts of Piotrków Trybunalski, where they destroyed 2 armoured cars and 6 tanks from the Wehrmacht's 1st Tank Division at the cost of one tank. On the next day, all three companies of the battalion attempted an attack on the 4th Tank Division, destroying a traffic column from the 12th Infantry Regiment and 15 tanks and armoured cars during the largest tank battle of the Polish campaign. At least 7 tanks were lost by the Poles. Due to overwhelming numerical superiority of the Germans, the Poles were forces to retreat.
Busting stereotypes of the Polish campaign: a Polish 7TP tank with German cavalry in the background.
Captured 7TP tanks were used in France (where they were discovered by Americans in 1944) and during anti-partisan operations in Poland, Lithuania, and Belarus.
Two or three damaged 7TPs were captured by the Red Army during the Soviet invasion. A complete tank was assembled from several non-functional ones and underwent trials at Kubinka in October of 1940. The diesel engine, gun mantlet, and Gundlach periscope piqued the interest of Soviet engineers, and these solutions were later used in Soviet designs.
7TP tank at an exhibition in Kiev.
The results of battles showed that the 7TP had equal chances when faced with German or Czechoslovakian gun tanks used by the Wehrmacht. The result of tank battles depended on non-technical factors such as surprise, numbers, crew training, commander experience, and unit synergy (some Polish crews were formed immediately before the war from reservists who had no experience with armoured vehicles). Another significant advantage was the widespread use of radio stations in the German tank forces.
The comparison with another participant of the events of September of 1939, the T-26, could also be interesting. The other descendant of the Vickers Mk.E was better armed (a 45 mm gun compared to a 37 mm one) and had two machineguns for auxiliary armament instead of one. The observation devices and sights of the 7TP were better. The Polish tank had a 110 hp diesel engine, while the Soviet one only had a 90 hp gasoline one. However, the effective power was about the same: the Soviet tank weighed 8 tons, 1.4-1.9 tons less than the Polish one.