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Based on a Vickers Armstrong 6 ton design, a popular product world wide, the 7TP was produced in Poland starting from 1931. Poland purchased 38 Vickers E tanks (22 twin turret and 16 single turret) for the Polish Army along with the license allowing Poland to produce them in Poland. The 7TP was considered a light tank by standards at the time. Some early models had 2 turrets, each mounted a machine gun. Later models had a single turret with a 37 mm cannon as shown above. The 7TP (with the 37 mm cannon) was more than a match for German Panzer 1 and 2, and an equal of Panzer 3's except in armor protection*. The German army was so impressed with this design they incorporated as many 7TP tanks as possible into their service.

Captured 7TP tanks in German service

*Late models had 40 mm of frontal armor. This made the tank stronger than the Panzer 3 of that period. In fact, the Germans lost a great deal of armor in the Polish campaign. That was one of the reasons for the "phony war" on the western front. Germany needed time to rebuild/repair their armor.

Warsaw September 1939 by David Pentland
Polish 7TP (Twin Turret) light tank of Captain F. Michalowski's training company breaks out from the street barricade to counter attack German reconnaissance elements.

Though Poland had limited industrial capacity, there was real interest in tank warfare and design. Sadly (and lucky for the Russians and Germany), the best designs had not reached production level prior to September 1939. The Polish army was equipped with less than 950 tanks in an odd mixture of imports, tankettes, and light tanks. This force had to face a German Panzerwaffe of over 3000. Soviet tank numbers are unknown.

The Poles were far ahead of many nations in tank development. Using the Sauer engine made the 7TP the worlds first diesel powered tank. The 7TP was the Polish version of the Vickers 6 ton (twin turrets) but with thicker armor (17 mm). This actually made the tank a 9.5 ton machine. In 1937 the unit was redesigned to a single turret with a 37 mm cannon. The final model of the 7TP had a larger turret and up to 40 mm of armor (welded). The model also included better suspension and wider tracks.

*Specifications*
Crew	3
Engine	Armstrong Siddley Puma 91.5 hp air cooled, or Swiss Sauer VBLDb 110 to 115 hp water cooled. Using the Sauer made the 7TP the worlds first diesel powered production tank.
Weight (battle)	11+ U.S. tons, 9.9 metric tons
Speed	22.98 mph
Range	150km (road) 130km (cross country)
Communications	7TPjw came equipped with N2C
Armament	7TPdw had 2 x Browning 7.92mm MGs. 7TPjw had 1 x 37mm Bofors and 1 x Browning 7.92mm MG.
Height	6.61'
Width	7.55'
Length	14.96'
Armor	5 - 18mm. Up to 40 mm (late models).
Power to Weight	11.1 bhp/ton
Track Ground Pressure	0.6kg/cm²

Additional Sources:

mailer.fsu.edu/~akirk/tanks/pol
derela.republika.pl
www.wargamer.com/articles/captured_tanks
www.military-art.com
www.wojmar.republika.pl

When the Wehrmacht blasted into Poland in 1939, their main opposition was the TK-3, the 7TP, and about 50 French-built R35’s. The TK-3 was a tankette (better known as deathtrap) armed with only machineguns, and proved easy meat for the Panzers.

The 7TP was another matter: this light tank was armed with a 37mm gun and was capable of defeating the Panzer I and II’s that made up the bulk of German armor at the time. The tank had a 110 hp engine producing a speed of 22mph with a range of 93 miles. Armor was 5mm-17mm, with a weight of around 10 tons. There was a crew of three, and armament other than the 37mm consisted of two 7.92mm machineguns.

The Poles had two battalions equipped with the 7TP, and after the capitulation, the Germans used as many as they could salvage. They were initially used as tanks for policing in occupied territories but were later converted to artillery tractors. Thus started the practice of applying the Black Cross to a vanquished foe.