Pz.Kpfw.I Ausf. B: All Grown Up

The creation of the PzI light tank did not come easily for German tank building. The tank was redesigned several times while still in the development stage, starting out as a 3 ton tank with a 20 mm autocannon, and ending up as a 5 ton tank, where nothing larger than a pair of MG-13 machineguns could fit into the turret. Even though the PzI entered production and became a mass produced tank, easily numbering over 1000 units, the German tank forces were not completely satisfied with its characteristics even before production began. Modernization was only a matter of time. What results did it bring?

Bigger engine

The Germans have no one to blame but themselves for the metamorphosis of the PzI during its creation. This was a chronic issue with the Wehrmacht; the only case where the initial requirements, especially the mass, coincided with the final product was with the B.W. support tank (PzIV). This happened not because of the military, but because of Krupp's engineers, who were initially only responsible for designing a turret for Rheinmetall's chassis. It just so happened that Krupp managed to push through a whole tank along with their turret. This tank ended up being the most numerous in the German army, remaining in service until the late 1960s.

As for the Kleintraktor/La.S., later indexed PzI, its creation can be considered a canonical example of a typical situation where the German military demanded that its engineers do the impossible. A 3.5 ton, 3.5 meter long hull was supposed to fit three crewmen, a 20 mm autocannon, an engine that provided 17 hp/ton, and reliably protect from rifle bullets. Even though the idea of a three man crew and a 20 mm autocannon were discarded during development, the tank's mass kept growing.

NL 38 Tr engine. Its installation meant a redesign of the PzI.

Meanwhile, the limited dimensions of the hull reduced the number of engines that could be installed in it. Krupp engineers had to take an opposite engine from a truck and beat it into shape. It's not surprising that issues with the engine began immediately. The first chassis only had a top speed of 34 kph. Tanks from the first series (1.Serie/La.S.) had improved engines, which increased the top speed to 37.5 kph.

Meanwhile, the mass of the chassis reached 4 tons, and the tank still had to get a turret, a turret platform, armament, and ammunition. Finally, the mass of the PzI Ausf. A reached 5.4 tons, and the power to weight ratio dropped to 11.1 hp/ton. Formally, the top speed remained the same, but there is no such thing as miracles. Engine trouble was common in these tanks.

The German military started thinking that things weren't exactly going to plan in the summer of 1932. On August 18th, Krupp received a letter from the 6th Department of the Armament Directorate, ordering them to urgently work out the possibility of installing the Büssing-NAG Typ G engine. This 3.92 L 65 hp 4-cylinder inline engine was installed on the Büssing-NAG G 31 family of trucks. Krupp's designers looked into the issue and replied with a distressing verdict. Installation of a water cooled engine required a complete redesign of the engine compartment and an increase in mass of 250 kg.

Despite all this, the issue of a new engine remained. Krupp initially decided to deal with it on their own. Work on a prospective 80 hp V-shaped 8 cylinder air cooled engine began in October of 1932. The first stage of the project was completed in November of 1932, and it was already clear that a hull redesign was still necessary. The hull needed to be 220 mm longer, mostly in the engine compartment. The output of the potential engine increased to 85 hp.

At the same time, the idea of installing another Büssing-NAG engine came up, this time an 80 hp one. In 1933, another competitor arrived on the scene, this time from Adler.

La.S.-May chassis. The suspension modifications are shown.

Finally, with the help of Ernst Kniepkamp, a new engine was found. A key employee of the 6th Department was working on halftracks. The 6 cylinder 90 hp 3.5 L NL 35 engine was designed at Maybach for one of them, the 5 ton Büssing-NAG BN L5. It served as the foundation for the 3.8 L NL 38 engine, which output 100 hp.

The idea of using this compact engine that showed itself well in a halftrack was reasonable. A tank version of the engine was ready by the end of 1935, indexed NL 38 Tr. This engine was chosen as the "heart" of the PzI.

Even though the new engine did not take up much space, a redesign of the hull chassis was still needed. One of the weaknesses of the PzI Ausf. A was its suspension. The installation of a new engine was sufficient reason for a redesign, especially since the engine was lengthened anyway. The number of road wheels increased to five per side, and a new idler was installed, lifted above the ground. This modification made the chassis, indexed La.S.-May, more stable. This later made it possible to develop SPGs on its platform.

PzI Ausf. B chassis diagram.

As for the fighting compartment, it was left mostly unchanged. The rear wall was altered since, the new engine compartment resulted in a new engine deck. The observation devices were removed from the back wall, since there was no more space for them. The turret platform lifting eyes were changed, and the bolts received bulletproof caps. The turret was changed even less. The lifting eyes were moved from the sides to the top, and the rivets were altered.

To training tanks and back again

According to plans from January 15th, 1936, the share of tanks with Maybach NL 38 Tr engines was not great: only 325 out of 1500. The final number was even smaller, since 72 tanks with the La.S.-May chassis were going to be used for commander tanks. Only 253 tanks out of the 5th series (5a.Serie/La.S) were left with new engines. 30 tanks with serial numbers 10478-10537 were assembled by Daimler-Benz. The biggest share fell to Henschel: 107 tanks with serial numbers 12501-12608. The second largest contract was filled by MAN: 66 5a.Serie/La.S. with serial numbers 13501-13566. Finally, Grusonwerk built 50 tanks with serial numbers 14501-14566.

5a.Serie/La.S. tanks in Poland, September 1939.

Production of the 5a.Serie/La.S. began in the summer of 1936. The precise date is currently unknown, but it likely happened in July or August. By October, 52 tanks were delivered to the army. Meanwhile, a contract for a second batch of La.S.-May chassis was on the horizon. These tanks were indexed 6a.Serie/La.S. On the outside, these tanks were distinguished by the reinforcement beam in the rear and three rivets on the driver's observation hatch.

146 tanks from 6a.Serie were built in total. Daimler-Benz received a small order for 30 tanks yet again, with serial numbers 10538-10567. The biggest order went to Henschel, which assembled 48 tanks with serial numbers 12609-12656. MAN and Grusonwerk received contracts for 34 tanks each, 13567-13600 and 14687-14720 respectively. The date of the start of production is unknown, but it's known when it ended. In May of 1937, all tanks were ready, and 58 were awaiting delivery. By then, tanks with the Maybach NL 38 Tr engine received the index PzI Ausf. B.

PzI Ausf. B, 6a.Serie/La.S. The rivets in the driver's observation hatch are shown.

Production of the PzI officially ended at this point. This is caused in part by reports from Spain about their use. These reports were not complimentary for the machinegun tank. It turned out that these tanks could not effectively fight T-26 tanks received by the Republicans. A tank armed with, at the very least, a 20 mm autocannon, was necessary. Such a tank, the La.S.100, was designed by MAN engineers and put into production in the fall of 1936.

Better known as the PzII, this tank replaced its machinegun-armed predecessor, further production of which seemed pointless. In reality, production of "number one" continued, although these vehicles were no longer officially called PzI Ausf. B.

Schulfahrzeuge, a learning tool for German tankers.

PzI tanks from the very first production run (1.Serie/La.S.) never received turret platforms or turrets, and were reclassified as training tanks. The military liked the idea so much that, in addition to proper tanks from 5a.Serie/La.S., Grusonwerk received a contract for 120 5b.Serie/La.S. vehicles.

Officially, they were called Schulfahrzeuge, or "school vehicle". This was simply a PzI Ausf. B with a railing instead of the turret platform. The engine deck was also slightly different: the lifting eyes were moved from the sides to the top, and it was made from mild steel.

These training tanks received serial numbers 14567-14686. A batch of 60 6b.Serie/La.S. tanks with serial numbers 14721-14780 followed, also built by Grusonwerk. The seventh series (7b.Serie/La.S.) was built by Henschel, who built 70 tanks with serial numbers 15201-15240. Finally, the eighth series (8b.Serie/La.S.) was split up between three companies. Damiler-Benz built 21 tanks with serial numbers 16001-16021. Henschel built 37 tanks, with serial numbers 16101-16137. The last 17 training tanks with serial numbers 16201-16217 were built at MIAG. In total, 295 Schulfahrzeuge were built.

A captured PzI Ausf. B. Judging by the lifting eyes on the sides of the turret, this is an Umsatz-Fahrzeuge.

As a rule, it is written that these tanks were built exclusively for educational purposes and did not participate in combat. This makes the PzI Ausf. B on display at Patriot Park look very interesting indeed. Its serial number, 16208, indicates that it was a training tank built at MIAG. Meanwhile, it carried a 5a.Serie/La.S. turret platform and a PzI Ausf. A turret. It is not known how many Schulfahrzeuge  were converted into tanks.

Converted tanks had almost no differences compared to regular PzI Ausf. B tanks.

While a tank from a museum might raise some questions, there is no doubt that PzI Ausf. B with serial number 14720 was not the last PzI with a turret and armament. After production of 6a.Serie/La.S., the military had an idea for an additional production run. This happened in rather interesting conditions. A number of PzI Ausf. A tanks outside of the aforementioned 150 1.Serie/La.S. were converted into training tanks via removal of turret platforms. This was done by the military, and the practice was rather widespread. Officially, conversion of the PzI Ausf. A into training tanks was permitted on October 2nd, 1937.

As a result, a reserve of turrets and turret platforms formed. The logical idea of releasing an additional batch of chassis was voiced. This resulted in a series of tanks that were not, formally, called PzI Ausf. B, but were almost identical to them (aside from PzI Ausf. A turrets). These tanks were called Umsatz-Fahrzeuge, or "converted vehicle". Their exterior was identical to the tank on display at Patriot Park.

Smoke grenade launchers like these were installed on tanks from the 101st Flamethrower Battalion. This unit had no PzI tanks, but similar launchers were often installed in neighbouring units.

The first contract for Umsetz-Fahrzweuge, indexed 7c.Serie/La.S., was signed with Grusonwerk in October of 1937. Later, the issue of building an additional batch of Umsetz-Fahrzweuge, 8c.Serie/La.S., was raised. Growonwerk received an order for only 9 tanks with serial numbers 16301-16309. Henschel received a much larger slice of the pie: 86 chassis with serial numbers 16401-16486.

The real number of La.S.-May tanks differs from the official number of 546 vehicles. One can count at least 546 tanks, and it is also not known how many PzI Ausf. B-like tanks were built from training tanks, like the one in Patriot Park.

Commander's box

The first command tanks on the PzI chassis were built in 1935. Overall, the idea of a conversion was deemed a good one. At the same time, experience showed that the leichte (Funk) Panzerwagen needed improvement. For starters, replacing the turret with an immobile casemate was just a half-measure. More space was needed inside for additional equipment. In addition, the commander's tank was completely unarmed, which could result in issues in battle.

Kleiner Panzerbefehlswagen from 7a.Serie/La.S.. The tank does not yet have a commander's cupola, and the machinegun port is covered up.

Discussion of a new series of commander tanks on the La.S. chassis began in the fall of 1935. On November 29th, during discussion of equipping tank units with new materiel, a decision was made to order 72 commander tanks. 47 of them would be built on the La.S.-May chassis. The tank received the name Kleiner Panzerbefehlswagen (small commander tank) and index Sd.Kfz.265. Its main difference from the PzI Ausf. B was the addition of a large casemate instead of the turret and turret platform. As with the leichte (Funk) Panzerwagen, the number of crewmen was increased to three.

Thanks to increased volume, the crew's working conditions improved noticeably. Large two-piece hatches were built into the roof and left side. The appearance of a machinegun ball mount in the front of the casemate was also an important addition. Thanks to this, the Kleiner Panzerbefehlswagen could stand its ground in a battle with infantry. The radio equipment included a Fu 2 (EU) transmitter and a Fu 6 two-way radio. Stable voice communication was possible over a range of 4-6 km.

Kleiner Panzerbefehlswagen with a commander's cupola of the first type.

The 47 commander tanks were combined into the 5a.Serie/La.S. run. One tank, serial number 12521, was built at Henschel. Grusonwerk received about a third of the order, 14507–14510, 14515–14517, 14519, 14520, 14522–14528, 16 in total. The biggest order went to Daimler-Benz. They assembled 30 Kleiner Panzerbefehlswagen with serial numbers 10478–1497, 10506–10512, 10514, 10518, 10522. In addition, Daimler-Benz produced casemates that were installed by other manufacturers.

This was not the end of Kleiner Panzerbefehlswagen production. Soon, an order followed for 112 7a.Serie/La.S. commander tanks. This time, Grusonwerk did not participate at all. Daimler-Benz built 44 tanks with serial numbers 15001-15044. Henschel was responsible for most of the order: 68 tanks with serial numbers 15101-15168. Production of the Kleiner Panzerbefehlswagen ended towards the end of 1937.

The final form of the Kleiner Panzerbefehlswagen (right). Poland, September 1939.

The Kleiner Panzerbefehlswagen underwent many conversions during its service. The most noticeable one is the introduction of commander's cupolas in place of the roof hatch. There were two types of cupolas, differing in hatches and peaks over the observation slits. In the end, all commander tanks were equipped with these cupolas.

A tank for battle

The combat debut of the PzI Ausf. B was in Spain, just like its predecessor. Thanks to an improved engine, the maneuverability of the tank increased. In addition, engineers managed to fix several design flaws. However, the improved maneuverability did not affect combat effectiveness. The tank was still armed with a pair of machineguns, and it was almost helpless against the T-26.

Pz.I Ausf. B in Spain.

The Germans knew the limitations of the PzI, but there was nothing to replace it with. Even though the military began receiving PzII tanks in 1937, these vehicles were transitional tanks. As for the PzIII, the tanks that were supposed to make up the core of the German tank forces, production was delayed. Only 10 PzIII Ausf. A tanks were built, and the PzIII Ausf. B-D were also few in number. As a result, out of 2553 tanks that fought in Poland, 973, or 38%, were PzIs.

A third of the tanks used in Poland were knocked out.

The result of a month of fighting was harsh. 320 tanks were knocked out, 89 were lost irreparably. The combat effectiveness of the PzI was low, and the saturation of the Polish army with anti-tank cannons and rifles drastically reduced its survival rate on the battlefield.

The real nightmare for PzI crews began in the spring. As of May 10th, 1940, German units fighting in France had 554 PzI tanks. By the end of the brief campaign, 182 tanks of this type were irreparably lost. If the PzI could hope to do something against TKS tankettes, they were useless against French tanks, most of which had 40 mm of armour. The Germans could have predicted this situation, but could not discard the PzI. By that point, there were not enough PzIII tanks, and the Panzerwaffe needed every tank they could get.

Out of 66 PzI tanks sent to Africa, there were only 11 Ausf. Bs. The situation on the Eastern Front was different. Ausf. A tanks did not end up here at all, but 337 PzI Ausf. Bs were available on June 22nd, 1941. By the end of August, 172 were written off. Several tanks were captured by the Red Army. Studies of the trophy ended with a technical description, as it did not cause any interest. The last PzI tanks disappeared from the front in 1943. By that point, they were only used as commander tanks.

Despite their obvious drawbacks, some tanks survived until 1943.

Overall, the PzI turned out to be a controversial vehicle. It was the first real mass produced German tank, but it was already obsolete as soon a it started production. The time of machinegun-only tanks was over by the mid-1930s. The Germans had a sober idea of the tank's abilities, indicated by a mass conversion of these tanks into training aids. After 1939, PzI tanks were used to build SPGs and other special vehicles, which deserve their own article.

Original article by Yuri Pasholok.