cruiser designs sacrificed armour compared to the infantry tanks. The Soviet fast tank (bistrokhodniy tank, or BT tank) classification also came out of the infantry/cavalry concept of armoured warfare and formed the basis for the British cruisers after 1936. The T-34 was a development of this line of tanks as well, though their armament, armour, and all-round capability places them firmly in the medium tank category. Flame tank A flame tank is a tank equipped with a flamethrower, most commonly used to supplement combined arms attacks against fortifications, confined spaces, or other obstacles. The type only reached significant use in the Second World War, during which the United States, Soviet Union, Germany, Italy, Japan and the United Kingdom (including members of the British Commonwealth) all produced flamethrower-equipped tanks. A number of production methods were used. The flamethrowers used were either modified versions of existing infantry flame weapons (Flammpanzer I and II) or specially designed (Flammpanzer III). They were mounted externally (Flammpanzer II), replaced existing machine gun mounts, or replaced the tank's main armament (Flammpanzer III). Fuel for the flame weapon was either carried inside the tank, in armoured external storage, or in some cases in a special trailer behind the tank (Churchill Crocodile). Flame tanks have been superseded by thermobaric weapons such as the Russian TOS-1. Modern Main battle tank Advances in tank design, armour, and engine technology allowed tank designers to increase the capabilities of tanks significantly, allowing vehicles to undertake multiple roles on the battlefield. This could be accomplished without always resorting to heavier designs, although weights did gradually increase. High-explosive anti-tank (HEAT) ammunition was a threat to tanks and could penetrate steel armour thicker than was practical to put on a tank. Advances such as the British-designed Chobham armour limit the effectiveness of weaker HEAT rounds, but the vulnerability still remained. On 7 November 1950, the US Ordnance Committee Minutes (OCM), order #33476, ceased utilizing the terms heavy, medium, and light tanks and redesignated tanks by the gun system, e.g. 90 mm Gun Tank M48 Patton, etc. with heavy gun tanks (), medium gun tanks (), and light gun tanks (), although these gun terms were often still shortened to simply heavy, medium, and light tanks. The term "main battle tank" (MBT), in the US, was first generally applied in 1960 to an all-purpose tank, armed and protected as a heavy tank, but with the mobility of