The engine on the Ausf.B was upgraded to 100hp, nearly double the 57hp of the Ausf. A. Also, it had a 40cm longer hull, and a pair of 7.92mm MG13 machine guns were equipped. While the Pz.Kpfw.I was developed for training, it first saw live action in Spain during the Spanish Civil War, and was widely used in various situations such as the invasion of Poland and the Eastern Front.