Of the many variables that take place during any conflict, supply and mobility are the most pressing. Germany realized this fact very early in World War 2 and demonstrated the use of support vehicles during their early "Blitzkriegs". They had developed a great number of vehicles for differing purposes, and a very successful one was the Sd.Kfz. 251 half-track. This semi-tracked vehicle became the centerpiece of their mechanized corps throughout the conflict. production began in 1939, and the series is broken down into four types, from Ausf.A to D. according to the differences in design and its production period. Early models used a very complicated hull construction, made up of obliquely placed armor plating. This was somewhat simplified in the C and D types, to make mass production easier. The final "D" version appeared in 1943, and it became the most widely used model of the four versions. Of the many types produced, the basic personnel carrier was the Dd.Kfz. 251/1. Powered by the Maybach HL42 six-cylinder engine, it had a top speed of 53km/h and a range of 300km. It was armed with two MG42 machine guns plus automatic rifles for the crew and could carry twelve fully equipped soldiers. This versatile half track was also the basis for a wide variety of self-propelled weapon systems, which were mounted to its chassis. More than 10,000 of the D-type half-track and its variants were produced.