tanks received a new designation, Panzerkampfwagen (PzKpfw or PzKw). The first machine to use this was the two-man PzKpfw I Ausf A, a 5.4-ton machine with a 3.5-litre petrol engine it had 13 mm of armour and was armed with twin 7.92 mm machine guns. The Panzer I light tank design began in 1932 and mass production in 1934. The more common Ausf B was a trifle larger to accommodate a Maybach engine. Both models were sent to the Spanish Civil War for testing, along with other new German weapons. From Spain it quickly became clear that the next generation of tanks would need better armour, greater range and much heavier weapons. 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. The Panzer I's performance in combat was limited by its thin armor and light armament of two general purpose machine guns. As a design intended for training, the Panzer I was not as capable as other light tanks of the era, such as the T-26. The PzKpfw II was around 50% heavier than the I and added a 20 mm Solothurn cannon as main armament as well as increasing maximum armour to 30 mm. In 1934, delays in the design and production of the Panzer III and Panzer IV tanks were becoming apparent. Designs for a stopgap tank were solicited from Krupp, MAN, Henschel, and Daimler-Benz. The final design was based on the Panzer I, but larger, and with the turret mounting the 20 mm anti-tank gun making it a more formidable tank than the Panzer I. Production began in 1935, but it took another eighteen months for the first combat-ready tank to be delivered. It was also sent to Spain from 1937, and the PzKpfw II proved more capable against light infantry, but no better when faced with capable anti-tank guns or other tanks. Despite these weaknesses production continued until 1941, at the outbreak of war the German Army had 955 PzKpfw IIs and almost 4000 were built in total. A major boost to German armour came with the acquisition of Czechoslovakia in 1938, giving the entire Czech arms industry to Germany. The Czechs already had two main tank designs, the Skoda LT35 and the Cesko-moravska Kolben Danek (CKD) TNHP. The Skoda was a 10-ton machine with a 37 mm main gun