The Panzer I was a light tank produced in Germany in the 1930s. The name is short for the German Panzerkampfwagen I (armored fighting vehicle mark I), abbreviated PzKpfw I. Design of the Panzer I began in 1932 and mass production in 1934. Intended only as a training tank to introduce the concept of armored warfare to the German Army, the Panzer I saw combat in Spain during the Spanish Civil War, in Poland, France, the Soviet Union and North Africa during the Second World War. Experiences with the Panzer I during the Spanish Civil War helped shape the German armored corps' invasion of Poland in 1939 and France in 1940. By 1941, the Panzer I chassis design was used for production of tank destroyers and assault guns. There were attempts to upgrade the Panzer I throughout its service history, including by foreign nations to extend the design lifespan. It continued to serve in the armed forces of Spain until 1954. The Panzer I's performance in combat was limited by its thin armor and light armament of two general purpose machine guns. Although weak in combat, it formed a large portion of Germany's tank strength in numbers and was used in all major campaigns between September 1939 and December 1941. The small, vulnerable light tank would be surpassed in importance by better-known German tanks. Nevertheless, the Panzer I's contribution to the early victories of Nazi Germany during the Second World War was significant.