The T-34 is a Soviet medium tank introduced in 1940, famously deployed during World War II against Operation Barbarossa. Its 76.2 mm (3 in) high-velocity tank gun was more powerful than its contemporaries while its 60 degree sloped armour provided good protection against anti-tank weapons. The T-34 had a profound effect on the conflict on the Eastern Front in the Second World War, and had a lasting impact on tank design. After the Germans encountered the tank in 1941, German general Paul Ludwig Ewald von Kleist called it "the finest tank in the world" and Heinz Guderian affirmed the T-34's "vast superiority" over German tanks. "As early as July 1941, OKW chief Alfred Jodl noted in his war diary the surprise at this new and thus unknown wunder-armament being unleashed against the German assault divisions." Although its armour and armament were surpassed later in the war, it has been described as the most influential tank design of the war.
The T-34 had well-sloped armour, a relatively powerful engine and wide tracks. The initial T-34 version had a powerful 76.2 mm gun, and is often called the T-34/76 (originally a World War II German designation, never used by the Red Army). In 1944, a second major version began production, the T-34-85, with a larger 85 mm gun intended to deal with newer German tanks. German military intelligence in World War II referred to the two main production families as T-34/76 and T-34/85, with subvariants receiving letter designations such as T-34/76A - this nomenclature has been widely used in the West, especially in popular literature. When the German Wehrmacht used captured T-34s, it designated them Panzerkampfwagen T-34(r), where the "r" stood for russisch ("Russian"). The Finns referred to the T-34 as the Sotka after the common goldeneye, because the side silhouette of the tank resembled a swimming waterfowl.