Like other world powers after World War 1, the Polish government moved on acquiring the popular British-originated Carden-Lloyd "tankette". In 1929, the military procured about ten Mark VI versions which would evolve the local, license-produced "TK" line. The lightweight, nimble and relatively inexpensive tankettes saw widespread service under a plethora of national flags including the Soviet Union and Japanese Empire.
Inevitably, thought turned to replacing the rather limited little systems amidst changing times in Europe. As such, the "4TP" light tank was being developed as a direct successor. The design included four road wheels to a track side, a front-mounted drive sprocket and a rear-mounted track idler. There were two track return rollers to manage the upper track portions. The chassis was covered by a fixed armored superstructure to house the crew and fighting compartment. A 360-degree traversable turret was set at the middle of the hull roof. The vehicle was crewed by two, a driver and commander - the commander doubling as his own gunner and loader and resided in the turret. The turret was fitted with a 20mm wz. FK-A main gun as primary armament as well as a 7.92mm wz. 30 TMG machine gun in a coaxial fitting. Dimensionally, the 4TP exhibited a length of 12.6 feet, a width of 6.8 feet and a height of 5.7 feet. It weighed 4.8 (short) tons. Armor protection was 17mm at the thickest facing.
Power for the tank was served through 1 x PZInz 425 4-stroke, 6-cylinder inline gasoline engine developing 95 horsepower. This supplied the hull with a top road speed of 34 miles per hour and an operational road range of 280 miles. Track wheels were suspended for cross-country travel.
The 4TP emerged in 1937 and was also known under the designation of "PZInz 140". Polish authorities were impressed enough with the indigenous design that they set an order for 480 examples to be manufactured. However, with the German invasion of Poland in September of 1939 to begin World War 2 (followed by the Soviet invasion a few weeks later), the 4TP initiative fell to naught.