In the decade of 1930 Poland bought between 40 and 50 British Vickers tanks of 6 tonnes. The later development of this model led to the construction of the 7TP light tank, which was in production from 1934 to 1939. The first version had two turrets, each of them equipped with a single machine gun, and it weighed about 9 tonnes. The engine was a Saurier of 110 horsepower. The subsequent version had, on the contrary, a Swedish turret armed with a Bofors 37-millimeter cannon and a co-axial 7.92-millimeter machine gun. Due to the difficulties in the supply of the Swedish turret, not many units of this model were built. The final version (the improved 7TP) had a heavier armor, a new turret designed on purpose and a more powerful suspension. However, it did not reach the production stage. The 7TP had to be replaced by the 10TP, whose first prototype was finished in 1937. It had a suspension of Christie type, and the engine was an American La France of twelve cylinders and 210 horsepower, which allowed the vehicle a top speed of 50 kilometers/hour in road. Like some American Christie tanks, the 10TP could also move on wheels, without using tracks. In such case, the top speed reached 70 kilometers/hour. The 10TP had the same turret than the 7TP, but besides it was armed with a machine gun installed in the hull. The 14TP was a medium tank which had as well a suspension of Christie type, albeit this model could move on tracks only. This tank reached a top speed of 50 kilometers/hour in road and it was moved by a German Maybach engine of twelve cylinders. Its combat weight was 14 tonnes. Like the 10TP, it never reached the production stage. The Polish ordered two American Christie tanks in 1936, but since they never paid them they were not delivered, and they were eventually incorporated to the United States Armed Forces. When the German invaded Poland in 1939, the Polish Army had an armored force of 169 7TP tanks as well as 50 Vickers of 6 tonnes, 67 French Renault FT-17 light tanks from the First World War, 53 Renault R-35 (which were withdrawn to Romania and did not enter action), about 700 TK/TKS tankettes and a hundred of armored automobiles. This force, sent to fight against more than 3000 Germans tanks, was quickly destroyed or captured.