Nazi Germany developed numerous tank designs used in World War II. In addition to domestic designs, Germany also used various captured and foreign-built tanks. German tanks were an important part of the Wehrmacht and played a fundamental role during the whole war, and especially in the blitzkrieg battle strategy. In the subsequent more troubled and prolonged campaigns, German tanks proved to be adaptable and efficient adversaries to the Allies. When the Allied forces technically managed to surpass the earlier German tanks in battle, they still had to face the experience and skills of the German tank crews and most powerful and technologically advanced later tanks, such as the Panther, the Tiger I and Tiger II, which had the reputation of being fearsome opponents. Panzer (ˈpænzər; ˈpantsɐ) is a German word that means "armour". It derives through the French word pancier, "breastplate", from Latin pantex, "belly". The word is used in English and some other languages as a loanword in the context of the German military. In particular, it is used in the proper names of military formations (Panzerdivision, 4th Panzer Army, etc.), and in the proper names of tanks, such as Panzer IV, etc. The dated German term is Panzerkampfwagen, "tank" or "armoured combat vehicle". The modern commonly used synonym is Kampfpanzer, or "battle panzer". The first German tank, the A7V of 1918, was referred to as a Sturmpanzerwagen (roughly, "armoured assault vehicle"). The German tank forces were a success especially due to tactical innovation. Using so-called "Blitzkrieg" ("lightning war") tactics, Heinz Guderian, Ewald von Kleist and other field commanders such as Erwin Rommel broke the hiatus of the Phoney War in a manner almost outside the comprehension of the Allied—and, indeed, the German—High Command. Basically, as a coherent unit, the combined arms tactic of the "blitzkrieg" shocked the Allies. Despite this, the German Panzer forces at the start of World War II appeared not especially impressive.