 Complete the following phrase:  Along with some improvised conversions, the three prototypes were formed into one unit and sent to first the Baltic and then to the Western Front. Conditions on both fronts were so bad that armoured cars could achieve very little, and the vehicles were eventually deployed on the Russian part of the Eastern Front, where they could at least use their mobility to some effect. It was then that there emerged a need for more vehicles, and so Ehrhardt was contracted to build a further 20 vehicles. These vehicles were 1.72 tons lighter than the original Panzerkraftwagen Ehrhardt 1915. Designated the Panzerkampfwagen Ehrhardt 1917, these vehicles were completed with revised frontal armour. The vehicles were sent to the Eastern Front and served there until the end of the fighting there late in 1917, two of them taking part in 