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.

*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.
 

     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.