 Complete the following phrase:  The first of the German armoured cars, the Sd.Kfz. 231 was based on modified Daimler-Benz, Büssing or Magirus 6x4 truck chassis. The 231 was armed with a a href220cm20KwK20302 cm KwK 30 L55a autocannon, and a Maschinengewehr 13 machine gun. It had a second drivers position in the rear so that the vehicle could be driven either forwards or backwards with relative ease. The 231 was introduced into service in 1932 and began to be replaced in 1937 when the German Army switched production to 8-wheeled armoured cars instead of 6-wheeled. Despite being replaced, they were used by reconnaissance units during the Invasion of Poland, the Battle of France, and the 