Friday 21 October 2022

Polish Tank Destroyer

The growth of tactical-technical requirements is a normal phenomenon for any army in the world. The brass also often doesn't know when to stop, which results in a strange metamorphosis. This happened to the tankette class of vehicles. Initially, the concept was something akin a mobile machine gun nest: a machine gun with a shield, engine, and tracks. Early tankettes were one-man vehicles, but experiments in the early 1920s showed that you need at least two crewmen. The Carden-Loyd Mk.VI is a classic example of this concept. Nevertheless, many nations quickly started treating it as a tank, albeit a small one. Requirements for these tankettes grew until they were more suited to tanks, and so the tankette withered away. 

TK-S tank destroyer, a great example of a successful modernization of an obsolete vehicle.

Poland was among the nations where the tankette lasted for much longer. These small AFVs made up the backbone of Poland's armoured forces. Of course, the army wanted something bigger and more heavily armed, but they had no other option. Over 650 TK family tankettes were built and actively used in September of 1939. Among them were two dozen tank destroyer tankettes armed with the nkm FK-A wz.38 20 mm autocannon. These vehicles were the result of work that began back in 1931.

A small support vehicle

The Polish army knew from the start that its tankettes were deficient. The issue of improving their armament was raised in August of 1931. Something more powerful than the ckm wz.25 (Ciezki karabin maszynowy wz.25 Hotchkiss, an improved variant of the French Hotchkiss Mle.14 machine gun) was needed. There were two solutions. One was the 47 mm gun that the British used. The resulting vehicle was a specialized machine that could be used for support or as a tank destroyer. Skoda was going to do something similar with the MU-4/I tankette that carried the 3,7/7 cm pěchotní kanón BA1/AB1 infantry gun. That vehicle was never built, but the Poles built four TKD tank destroyers. 

wz.30 Hotchkiss heavy machine gun, the first attempt to improve the TK's firepower.

The result had its advantages and drawbacks. The 47 mm gun was clearly too heavy for this chassis. The Polish military understood this, and a second solution was proposed in 1931. The idea consisted of installing the nkm wz.30 Hotchkiss machine gun (Polish version of the French 13.2 mm Hotchkiss Mle.1930). The same machine gun was supposed to be installed into twin-turreted Polish Vickers Mk.E tanks. 16 of these tanks got this machine gun in 1933, but they left much to be desired. Trials showed that the armour penetration was lacking, and so work on the machine gun was cancelled in 1934.

A TK-S tankette with a Swiss 20 mm semiautomatic Solothurn S18-100 gun.

The cancellation of the machine gun project didn't mean that this was the end. Orders to install an even more powerful weapon were given in May of 1935. This was a Swiss 20 mm semiautomatic Solothurn S18-100 anti-tank rifle. It was Swiss only on paper, since it was designed by Louis Stange, a famous German arms designer. The Solothurn S18-100 project also grew into the Flak 30 AA gun. There was also a fully automatic variant of the rifle used in an AA role. Installing such a large weapon into the TK-S was not an easy task, since the overall length of the rifle was 1900 mm, more than two thirds of the length of a TK-S.

The gun fit after all.

A new mounting had to be designed in place of the ckm wz.25 ball mount. The rifle was mounted in a frame that fit into an immobile mantlet. A hemispherical external gun shield was held on with bolts. The rifle fit into the tankette. There were no issues with reloading. The 5 round magazine could be comfortably inserted from the left.

The biggest issue was the low rate of fire of the Solothurn S18-100.

The tankette armed with a Solothurn S18-100 gun was submitted for trials in February of 1936. Trials showed that the experiment was a success. The gun penetrated a 20 mm armour plate from 200 meters. The gun mount was quite comfortable. The biggest problem was the rate of fire of only 4-5 RPM. There was an alternative, the fully automatic S15-100 system, but it was twice as heavy and 35 cm longer.

Trials of the nkm FK-A wz.38 machine gun.

A series of low caliber autocannons were tested in 1936-37, including Oerlikon, Solothurn, Madsen, Hotchkiss, and Hispano-Suiza models. Even the French 37 mm SA 18 was tried, but that variant was quickly rejected. Each gun turned out to be unsuitable. Either the dimensions were too big, or the rate of fire was too low, or both. It turned out in the end that the creation of a new autocannon was the correct solution.

The gun was installed in a TK-3 tankette in late 1938.

A 20 mm autocannon was developed under the direction of Bolesław Jurek in 1937. It was officially designated as a heavy machine gun (nkm, or najcięższy karabin maszynowy), but it was really an autocannon. The gun was initially ordered by the Polish air force, but they later declined it. Fabryka Karabinów in Warsaw quickly found a new buyer. The gun could quickly be adapted for the 20 mm Oerlikon (2 cm Flak 38) mount. The tankers also noticed this new arrival. An order was given in 1937 to adapt the gun for installation into a TK-S.

The front of the vehicle had to be altered.

The prototype with an autocannon was ready in late 1938. The gun was indexed nkm FK-A wz.38 (heavy machine gun, Fabryka Karabinów, model A, 1938 pattern). Since the nkm FK-A wz.38 was longer than the Solothurn S18-100, the front of the TK-3 tankette that it was installed it had to be altered. The right side of the transmission access hatch was removed and the casemate was enlarged. The mounting was similar to the one used for the Solothurn S18-100. The gun shield was now cast and the sight moved to the right. The gunner/commander's periscopic sight was moved to the left. 

 nkm FK-A wz.38 mount in a TK-S tankette.

Trials held in the winter-spring of 1938 showed that the nkm FK-A wz.38 was quite adequate for its purpose. Changes to the front of the TK-S hull were rejected. It turned out that the nkm FK-A wz.38 fit into a stock TK-S, albeit with issues. The use of stock tankettes would speed up the rearmament process.

Overrated improvement

The final decision to rearm TK-S tankettes with the nkm FK-A wz.38 autocannon was made in May of 1939. A second batch of 100 guns was ordered at the same time. 150 tankettes would be converted into tank destroyers: 80 TK-S and 70 TK-3. Conversion of a TK-S cost 34,000 zloty, conversion of a TK-3 cost 35,000. The conversions would be done in small batches since the capacity of PZInż and other subcontractors were limited.

Modernized tankettes from the 10th Armoured Cavalry Brigade. It received 8 of these vehicles.

The final version of the tank destroyer tankette did not differ much from the stock TK-3/TK-S. The gun mount was changed and the commander/gunner's periscope was moved. The nkm FK-A wz.38 was fed from 15 round magazines. On paper, the tank destroyer tankette looked good. Its gun could penetrate 40 mm of homogeneous armour at 200 meters or 40 mm of surface hardened armour at 300 meters.

Hungary ended up with some of these tankettes.

The biggest problem was that the Polish army was fighting against the clock. Only 24 tankettes were reamed before the start of the war (14 from the June order and 10 from the July order). It's possible that PZInż (Ursus) managed to put some together during the war. In any case, two dozen tankettes meant nothing. The handful that were made were assigned as reinforcements to regular TK-S units. 

Hungary captured 9 TK-3 and 7 TK-S tankettes, at least 3 of which had nkm FK-A wz.38 guns.

At first, a squadron of 13 tankettes would include 5 with nkm FK-A wz.38. Since the war was inevitable, a decision was made to spread the tankettes out among more squadrons, reducing the number to 4 each, giving enough vehicles for 6 squadrons. The biggest number (8 each) ended up in the 10th Armoured Cavalry Brigade and the Warsaw Motorized Brigade.

Most of the tank destroyer tankettes of the 10th Armoured Cavalry Brigade ended up at the disabled vehicle yard in Tomaszów Lubelski. Interestingly enough, none were taken during a Soviet raid on October 6th, 1939.

The most famous vehicle of this type belonged to a reconnaissance platoon of the 71st Tank Battalion of the Grand Poland Cavalry Brigade. This is due to the success of the crew commanded by Sergeant Edmund Roman Orlik. He was one of the few who managed to exercise the potential of his tank destroyer. Orlik's crew scored its first kill on September 14th, 1939, during an attack at Brochów. His most famous battle took place on September 18th near Warsaw. The battle was happening in a forest and Orlik successfully organized an ambush near a road. His crew caught a column from the 6th Tank Division, shooting up two Pz.Kpfw.35(t) tanks and one Pz.Kpfw.IV Ausf.B. The latter was commanded by Wiktor IV Albrecht von Ratibor. Orlik hit the tank's side ammunition rack, causing a detonation. The death of a German noble was an uncomfortable fact for German propaganda.

Pz.Kpfw.IV Ausf.B tank commanded by Wiktor IV Albrecht von Ratibor, destroyed by a TK-S tankette commanded by Sergeant Edmund Roman Orlik.

In total, Orlik claimed the destruction of 13 tanks. Even if the real number is much lower, he would still qualify as a tank ace. Orlik's fame is well deserved, but his success sometimes leads to the overestimation of the nkm FK-A wz.38 gun. The number of destroyed tanks was the result of Orlik's luck and bravery. Most other vehicles of this type could not realize their potential. Some of the vehicles of the 10th Armoured Cavalry Brigade slipped away into Hungary, most were either destroyed or captured by the Germans.

A captured tankette displayed in Berlin, spring 1945.

If the Polish army had the full 150 tankettes, it could bloody the nose of the German army. At the same time, it's important to not overestimate the vehicle's potential. The nkm FK-A wz.38 could penetrate the front of German medium tanks at point-blank range, as the Pz.Kpfw.III and Pz.Kpfw.IV had 30 mm of surface hardened armour. The TKS-D tank destroyers were much more effective, but they did not go into production. This was a mistake. This vehicle would have had no problems in production and would have been quite mobile and small. Most importantly, it would be able to defeat any German tank at medium ranges. However, Polish brass was obsessed with perfectionism.

This tankette was restored by collector Jacek Kopczyński

A number of these tankettes fell into German hands. They were repaired at the Ursus factory until it was repurposed for Pz.Kpfw.II production. Captured tankettes were used by police units. Later they were written off. Not a single TK-S with the nkm FK-A wz.38 gun survived. Polish collector Jacek Kopczyński recently restored a TK-S from fragments. This vehicle is often seen in historical reenactments.

Original article by Yuri Pasholok.

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