A flame tank is a type of 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). Combat effectiveness In comparison to man-portable flamethrowers, flame tanks carried much more fuel, and could fire longer-ranged bursts. Due to their ability to get in range of enemy positions in comparative safety, they were invaluable for rooting out heavy infantry fortifications. For example, as the main guns of US tanks were largely unsuccessful in penetrating the thick bunkers created by the Japanese defenders on islands such as Tarawa or Iwo Jima, flame throwing tanks were used instead while infantrymen provided the necessary security during their deployment. On Iwo Jima the marines learned that conventional firearms were relatively ineffective against the Japanese defenders and effectively used flamethrowers and grenades to flush out Japanese troops in the tunnels. One of the technological innovations of the battle, the eight Sherman M4A3R3 medium tanks equipped with flamethrowers ("Ronson" or "Zippo" tanks), proved very effective at clearing Japanese positions. The Shermans were difficult to disable, such that defenders were often compelled to assault them in the open, where they would face the full firepower of marine rifle and machine gun fire. The maximum range of a flamethrower was typically less than 150 metres. Because of this limitation, the flamethrower was virtually useless on an open battlefield. However, they proved a potent psychological weapon against fortified troops. In many instances, troops surrendered or fled upon seeing a flame tank fire ranging shots, rather than risk being burned alive. Experience of combat use of flamethrower tanks was mixed. German flamethrower variants of the Panzer II and Panzer III were both discontinued due to unsatisfactory performance and converted into assault guns