Searching for a new light tank
After 1919, Poland had relied on French FT light tanks for home defense, coupled with dozens of armored cars. But this was to change in 1931, when a modernization effort was put in motion, and the army considered several designs. Alongside the Carden-Lloyd Mk.VI, which already led to the successful TK tankette series, specifications asking for a bigger frontline tank led to the study of the American M1930 Christie and the British Vickers Mk.E designs. After the transactions with USA failed, the choice turned to Vickers, whose tank had already attracted the Soviet delegation (and was the inspiration for the T-26).
In 1930, the Polish delegation signed a contract for the supply of 50 tanks, of which 12 were to be assembled at home under licence. Although the first vehicle made a positive impression, a number of disadvantages were soon found, including a sensitive (even unreliable) and overheating engine, weak armament and protection and insufficient speed. In addition, the cost of a single Mk.E was equivalent to 180,000 zlotys, making the Polish Government cancel the order in 1931 and develop its own model based on the Vickers design.
Design and development of the 7TP
Work on an indigenous design started in late 1932, performed by the design bureau of armored vehicles of the Military Engineering Research Institute and the State Engineering Enterprises (PZInż). A contract for the delivery of the first batch was signed on January 19, 1933, but the initial design was not completed until June 24.
The suspension was left nearly untouched, comprising a front drive sprocket, a rear idler wheel, four doubled return rollers and two leaf sprung bogies with two sets of small roadwheels on each side of the tank. Each track was composed of 109 steel links, 267 mm (10 in) wide.
As the prototype had a twin-turret configuration, this was left unchanged, but since the chosen engine was almost twice as big (and powerful) as the original Meadows, the rear compartment was completely rebuilt. The hull, although still riveted, was also strengthened. The front plate rose to 17 mm (0.67 in) and sides up to 13 mm (0.51 in). The armament consisted of two wz.30 7.92 mm (0.3 in) machine guns, one for each turret. These had a rate of fire of 450 rpm, a maximum range of 4500 meters (2.79 mi) and a muzzle velocity of 735 m/s. The engine was a locally built diesel Saurer VBLDd, 6-cylinder, 1800 rpm, liquid-cooled, with a dry multidisc 4 forward and 1 reverse speed gearbox, belt brakes and final drive transmission. This was a reliable engine, providing enough torque to compensate for the added weight, excellent traction, speed over difficult terrains and good autonomy. The consumption figure was 80 liters/100 km, with two tanks for a total of 130 liters.
The 7TP dw
“dw” stands for “dwuwieżowy” (twin-turret). This was a feature of the original British design. Back then in 1930, multi-turreted tanks were favored. The two licensed Browning machine-guns had armor-piercing rounds (8 mm at 200 m). Each turret had 280° traverse and -10° to +20° elevation. The housing for each machine-gun was designed to easily replace the Browning wz.30 with a Hotchkiss wz.35 or a Maxim wz.08 instead. The driver was located in the front-right part of the hull, the commander took place in the right turret and the gunner on the left. Each turret had two vision slits with armored glass and telescopic sights. The driver had a front double door hatch, which also comprised a vision slit. Four prototypes were built largely of iron rather than steel, and designated VAU-33 (“Vickers-Armstrong-Ursus” or “Vickers-Armstrong Ulepszony”, factory designation – PZInż.120). The first delivered (called “Smok” or “Dragon”, serial number 1595) began trials in August 1934. These trials lasted until September 1, totaling 1,100 km (680 mi). The second prototype (“Slon”, No. 1596), was delivered on August 13, 1935. After this, two more were ordered, then designated 7TP (for “7-Tonowy Polsky”) or “seven ton tanks”. These twin turret 7TPs were later produced to an extent of 24 machines. They were considered a stopgap model, before the more powerful single turret version could be introduced. Rearmament tests included a 13.2 mm (0.52 in) Hotchkiss and a 7.92 mm (0.3 in) wz.30, and a total of 16 dw were rearmed according to this new “asymmetric” model. The penetrating power of the heavy machine gun was intended to deal with other light tanks and most armored cars. Later, a few were equipped with RKBc or N2C radios with mast antennae. Communication range was respectively 6 and 25 km (3.7-15.5 mi). They were given to platoons, companies and battalions command tanks.
The 7TP jw
“jw” stands for “jednowieżowy” (single-turret). This version was studied since 1934 and was to be the main 7TP production type. Development of a working prototype was slowed down due to issues with the main turret and spanned the years 1934-1936. At least six options were considered, including the Czech 47 mm (1.85 in) “Bullet gun”, the 55 mm (2.15 in) ZS, 47 mm (1.85 in) Rogla, 40 mm (1.57 in) L/55, Vickers AT 40 mm (1.57 in) and a licensed 37 mm (1.46 in) Bofors. Requirements asked for compact size, high rate of fire, the ability to penetrate standard armor for the time (up to 30 mm/1.18 in) and, most importantly, reliability. After eliminating the other options, the Swedish 37 mm (1.46 in) Bofors was chosen. After the terms of the contract were settled, Bofors not only provided the gun, but also the turret and all its equipment.
Work started in December 1935 and by November 1936 the first complete turret was delivered. However, the Poles refused these models and began to develop their own set of modifications. The changes affected the turret rear storage and location of the batteries. The frontal part and mask was 15 mm (0.59 in) strong and the roof had a thickness of 8-10 mm (0.31-0.39 in). Due to these modifications, the turret was slightly shifted to the left side. These turrets also counted a rear niche, serving both as a counterweight and to house the N2C RKBc radio, which was installed in the autumn of 1938 on 38 machines, intended for tank commanders. Additional ventilation holes were also added to the crew compartment. The Swedish 37 mm (1.46 in) Bofors could penetrate 60 mm (2.36 in) of armor at 300 m (984 ft), 48 mm (1.89 in) at 500 m (1640 ft), 30 mm (1.18 in) at 1000 m (3280 ft) and 20 mm (0.79 in) at 2000 m (6561 ft). Each shell weighed 700 g and was launched at 810 m/s. Practical range was 7,100 meters (4.4 mi) with a 10 rpm fire rate. It was provided with 80 rounds and paired with a coaxial 7.92 mm (0.3 in) wz.30 encased in an armored shell, fed with 3960 rounds.
Production progressed slowly, due to intermittent deliveries of modified Bofors turrets. The LCz-1×30 viewfinder, periscope observation devices wz.37 and periscopes wz.34 had to be supplied locally. The last were delivered in the February of 1939. A fifth order for 18 single-turret tanks was scheduled for May 1939, but at that time the next more modern 10TP and 14TP cruisers were already in the development phase. Due to a degrading international situation, however, the Polish government ordered, in April 1939, a further 32 7TP tanks to be delivered before the 30th of September. Further increases in production capacity meant that plans for new orders were scheduled up to December 1939 and early 1940, letting the Polish army hope to take delivery of at least 282 tanks.
Design modifications and variants
Work on a modernized version, the 9TP, started in 1938 and two versions were planned. The first one had a 40 mm (1.57 in) Bofors gun, and the second a more powerful gun, yet undecided. The 9TP had a diesel Saurer CT1D/PZLInż.155 engine, enhanced suspension and wider tracks. Although they never saw action, by the summer of 1939, 11 9TPs seem to have been delivered. Drawings show attempts to adapt a twin 20 mm (0.79 in) FK-A wz.38 L/73.5 on a 7TP, but no prototype was ever completed. The main fault of the 7TP was its limitations for successful modernization. The basic design was ten years old when the war started. Exports were also considered, to Estonia (4 units in 1937 – finally refused), Turkey (by 1938, under licence, but the contract failed due to the beginning of the hostilities), Yugoslavia and Greece (36 more).
However, its chassis was still good enough to be used as the basis for a prime mover. In 1933, two prototypes were built – the S6R and S6T. The first one featured a front engine and front wheel drive, both prototypes had a 115 hp PZlnż.235 diesel, and the turret was replaced by an armored cabin for the driver and a mechanic. For mass production the S6R was chosen, modified and renamed S7R (Ciagnik Siedmiotonowy Polski – 7-ton truck Polish). Until September 1939, 151 of 350 tractors ordered were delivered and put into service. These tractors were mainly used to carry Skoda 220 mm (8.66 in) mortars, and 18 S7R were put at the disposal of the 10th Cavalry Brigade for the transport of tanks and tankettes to the battlefield on special platforms. Captured units served with the Wehrmacht well into the end of 1941.
The 7TP in action
According to 1936-1942 plans, the Polish Army hoped to create eight battalions of light tanks. The first four prototypes released in 1934 were sent to the 3rd Battalion stationed in Warsaw. In less than six months it had received 14 more tanks, and the 4 preseries machines were given to the 11th Training Battalion training center at Modlin. In 1938, this unit took part in the first exercises at Volyn. On September, 1, 1939, the 1st Battalion of Light Tanks was part of the “Prusy” army with 49 7TPs. They were heading to Wrocław, but immediately deployed in the direction of Torun and later placed under general R.Dresheru. On the 6th of September the first clash with German tanks ended as a draw. The morning of September 7, the battalion supported the 13th Infantry Division, but were spread into separate units of the division. At the battle on the river Dzhevichke some managed to knock out three German tanks for the loss of two, while the 2nd company claimed seven kills against three losses. Later on, the 2nd Battalion began to gradually fall back to the rear, but still trying to support the infantry in the meantime. By September 9-12, the main force of 24 tanks, consisting of a third company and individual platoons of the 1st and 2nd TB, took part in the defense of the Vistula and Pilica rivers. Seven tanks under the command of Captain Gursky, supporting the 44th Infantry Regiment, managed to knock out and even capture a dozen German tanks and vehicles, but due to the lack of fuel, they had to be scuttled prior to retreat. Six other 7TPs of the 2nd company had to be flooded into the Vistula.
The third company departed on September 13 from Garwolin-Ryki and joined the “Lublin” army. They were sent to the Warsaw Bron-Motorized Brigade, taking part of the first battle of Jozefow. By the morning of September 18, captain Kossobudzsky was ordered to support the remaining 22 tanks from the 3rd Company of the 1st Infantry Regiment and wrecked six tanks, four armored cars and 8 other vehicles. After a 14 hour battle, the Poles were still holding the perimeter, but were also affected by the lack of fuel and spare parts, and crew exhaustion. By the morning of September 19, the retreat was ordered with seven 7TP, one Vickers Mk.E and four TKS left. The last coordinated attack was made in the area of Roguzhno with 5 7TP lost, and the remaining two scuttled on September 20 by their crews. The 2nd Battalion also had 49 tanks and took part in many actions, the last being evacuated into Romania.
Operational records of the 7TP show 70 lost in combat, 20 captured by the Germans, 1 by the Red Army, 13 broke down and 20 were interned by the Romanian authorities. In German service, 7TPs were repainted in dunkelgrau and participated in the “victory parade”, which was held in Warsaw on October 8, 1939. The 4th Company of the 1st Tank Regiment, 1st Armored Division, which fought in France in May-June 1940 was equipped with the 20 7TPs, later transferred in Norway, with the exception of one company left in France. The remaining were used for police duties in the occupied territories, in Poland and Ukraine up to 1944.
7TP jw specifications
|Dimensions||4.99 x 2.41 x 2.16 m (16.37×7.9×7.08 ft)|
|Total weight, battle ready||9.4 tons|
|Crew||3 (commander, gunner, driver)|
|Propulsion||Saurer VLDBb (PZInż.235) diesel 6-cyl., 110 hp (80 kW), 11 hp/ton|
|Suspension||Leaf sprung bogies|
|Max speed (road/off-road)||37-30 km/h (23-18.5 mph)|
|Range (road/off-road)||150-130 km (93-81 mi)|
|Armament||37 mm (1.46 in) Bofors Wz.37 L/45 gun
Coaxial wz.30 TMG 7.92 mm (0.3 in) machine gun
|Armor||From 5 to 17 mm (0.19-0.67 in)|
|Total production (jw)||108 (132 ?)|
7TP dw or “twin turret”, 1st Company of Light Tanks, involved in the defense of Warsaw, Okęcie Airport sector, 10-11 September 1939.
7TP single turret, 2nd Company of Light Tanks, Wola sector, 13 September 1939.
A 7TP with the “checkerboard-style” pattern, 2nd Light Tank Battalion, Łódź Army, Battle of Włodawa, September, 15, 1939.
7TP of the 1st Light Tank Battalion (Prusy Army), with the standard “horizontal pattern”, Battle of Głowaczów, 9-10 September 1939.
Captured German 7TP or Pz.Kpfw. 7TP 731(p), which served in France in May-June 1940, and later in Norway. Others were sent for police and anti-partisan warfare in occupied territories, like in Belarus and Ukraine.
Sources, influences : Thierry Vallet (www.kameleon-profils.fr), Adam Jonka, various photos.
7TP video (2011 public demonstration)
Credits : WaderaStudio.