The tank force consisted of two armored brigades, four independent tank battalions and some 30 companies of TKS tankettes attached to infantry divisions and cavalry brigades. A standard tank of the Polish Army during the invasion of 1939 was the 7TP light tank. It was the first tank in the world to be equipped with a diesel engine and 360° Gundlach periscope. The 7TP was significantly better armed than its most common opponents, the German "Panzer" I and II, but only 140 tanks were produced between 1935 and the outbreak of the war. Poland had also a few relatively modern imported designs, such as 50 Renault R35 tanks and 38 Vickers E tanks.