Overview
The 4TP, also known by the factory designation PZInż 140, was a Polish attempt to replace the limitations of the tankette with a small turreted reconnaissance tank. Accounts describe a single two-man prototype, tested before the Second World War but never placed in series production. Its significance lies in the development and evaluation of a domestic design, not in an operational career that the available research does not establish. Sources
The vehicle belongs beside, rather than inside, the history of the amphibious PZInż 130. Both emerged from a program using related automotive components, but they addressed different movement requirements. Proposed weapon fits and engine improvements likewise differ from additional tanks. Published accounts give disagreement about whether the prototype actually received its intended 20 mm cannon during testing; a photograph of an unarmed vehicle cannot resolve the whole trial history. Sources
Requirements and development
Poland's reconnaissance problem combined limited resources with dissatisfaction over the restricted protection, observation and armament of its existing tankettes. A turret offered a different means of employing a weapon without turning the entire hull. The program also sought greater domestic control over design and manufacture, while common engines and related components promised practical advantages across several proposed vehicles. Sources
Accounts associate development with Edward Habich and PZInż. British demonstrations in 1932 form part of the background, but is distinct from a license to manufacture the 4TP. The principal domestic work belongs to 1936–1937. Sources differ over the exact December 1936 documentation date; the prototype's transfer for military testing is placed in August 1937. These stages are not a service-introduction date. The later trials and changing procurement priorities are essential to explaining why a promising experiment did not become an ordered production fleet. Sources
Layout, protection and observation
The design placed the driver on the left side of a compact hull and the engine on the right, with a small one-man turret above the fighting compartment. The second crew member had to combine command, observation and weapon duties. Sources
Reported armor thickness ranges from thin floor and roof plates to approximately 17 mm at the thickest points. Accounts differ over construction terminology and the placement of a Gundlach-type periscope. Exact crew responsibilities, periscope installation, and a standard radio fit are not established in the cited material. Sources
Armament and equipment alternatives
The intended fighting arrangement combined a 20 mm automatic weapon with a 7.92 mm machine gun. The published ammunition figures—about 200 cannon rounds and 2,500 machine-gun rounds—belong to the proposed configuration. They are not a verified combat load carried by an operational unit. Reports that an FK-A cannon was fitted during summer 1938 conflict with accounts describing the prototype as never fully armed, so published accounts describe that uncertainty. Sources
Engine descriptions also remain uncertain. The strongest reading in the references identify a PZInż 425 petrol engine, approximately 3.88 liters and 95 hp, while cylinder-count descriptions conflict. A more powerful PZInż 725 appears in proposed-improvement material, but its installation is not established here. An alternative engine and a briefly mentioned flamethrower proposal are not established as completed production variants. Sources
Mobility and trial evidence
The reported specifications give a weight of approximately 4.33 tonnes, with a rounded 4.5-tonne value also present in the available evidence. Length and width are about 3.84 and 2.08 meters. Height varies between accounts. The listed road speed of roughly 55 km/h and quoted road and cross-country ranges are reported claims, not measurements assumed to apply under every condition. Sources
The test narrative includes an approximately 1,861 km autumn rally and a reported cumulative distance around 4,300 km by May 1939. These are useful leads into the evaluation record, but the underlying logs remain to be checked. Suspension softness and swaying are particularly important: comfortable movement or good speed did not automatically produce a steady firing platform. Accounts describe favorable judgments coupled with recommended repairs or changes, not an unconditional declaration of readiness for immediate mass production. Sources
Production plans, service and fate
Only one completed 4TP prototype is established in the available accounts. A figure of 480 vehicles occurs in modernization planning, but is not proof of a completed purchase, an active production line or 480 tanks built. Factory cost material is equally qualified: a quoted expenditure connected to three prototypes cannot simply be divided into a reliable production unit price without establishing exactly which projects and costs it included. Sources
The operational record is limited to evaluation. There is no supported combat history, foreign service fleet or series-production variant tree. Possible post-1939 fate claims remain uncertain. Its hypothetical reconnaissance value can be discussed as design assessment, but does not establish a narrative of units fighting with it. The 4TP demonstrates an indigenous attempt to balance mobility, a turreted weapon and manageable size; it also shows how testing, procurement priorities and the calendar constrained the transition from a prototype to a deployable system. Sources
Preservation and reference use
The available evidence does not establish a surviving original tank. The principal photograph shows the prototype without its intended weapon installation and is useful for its side profile and general running gear. Its unidentified photographer, uncertain date and limited reproduction history constrain finer claims about particular testing stages. Sources
The 4TP, 7TP, contemporary tankettes, and amphibious PZInż 130 addressed different requirements rather than forming one interchangeable class of vehicle. Sources
Sources and further reading
Background reading and references. Each photograph has its own source and credit.
- Baker 2020. Bernard Baker, “PZInż. 140 (4TP),” Tank Encyclopedia. Tank Encyclopedia. URL / reference:. Notes: Detailed secondary article; especially useful for development sequence, trials, layout, armor figures, planned armament, and production-cancellation narrative. Uses Janusz Magnuski, Piotr Zarzycki, A. Jońca, and other Polish secondary sources
- Michał Derela / PIBWL. “Polish light tank 4TP (PZInż 140)” and Polish-language companion page. Polish Armour 1918–1939. Further reading. Source
- Michał Derela / PIBWL. “Polish light tank 4TP (PZInż 140)” and Polish-language companion page. Polish Armour 1918–1939. Further reading. Source
- Armor Archives 2019. “The Polish Army’s Phantom Reserves,” Armor Archives. Armor Archives. URL / reference:. Notes: Detailed secondary article useful for tankette replacement context, Vickers/Landsverk influence, proposed 480-vehicle program, comparative observations, and source-conflict checks
- pl. “Zamiast tankietek. Czołg 4TP PZInż.-140,” Kampania Wrześniowa 1939.pl. 1939.pl. URL / reference:. Notes: Polish-language secondary summary; useful for specifications and the replacement-of-tankettes framing. Direct page fetch was unreliable, so it is
- Commons 4TP. Wikimedia Commons, “File:4TP.jpg”. Wikimedia Commons. URL / reference:. Notes: Source for the embedded image. Commons marks the image public domain under Polish and U.S. conditions, but also flags missing source/author details
