From Wikipedia: “Einheits-PKW der Wehrmacht-literally:standardized military (passenger) cars was the Nazi German plan for a new, multi-purpose fleet of four-wheel drive, off-road capable and light trucks, based on just three uniform chassis, specifically designed and built for the Wehrmacht, formulated in 1934, and built from 1936 to 1943.
The new, standardized military vehicles were intended to replace the diverse fleet of two-wheel drive, militarized civilian vehicles, previously procured by the Reichswehr, predecessor of the Wehrmacht – with new cross-country mobile vehicles up to military requirements, that should simplify logistics, maintenance and training, by the use of standardized components.