Tundra tanks are large armored vehicles manufactured by the Fire Nation. These massive machines were first utilized by Fire Nation soldiers during the battle for the Northern Air Temple. Tundra tanks were widely used by the Fire Nation for various war ventures during the Hundred Year War.
The tundra tanks' first known use was during the battle for the Northern Air Temple. They were likely designed by War Minister Qin and his unwilling accomplice, the mechanist. This was evidenced by the fact that tank wheels were present in the Northern Air Temple sanctuary, which was converted by the mechanist into a workshop where he also kept an early prototype of the war balloon. The mechanist only agreed to help Qin design such vehicles in exchange for the safety of his people, who took refuge in the abandoned Northern Air Temple following the flooding of their native village. When Aang and his group arrived and forced the mechanist to break his deal with Qin, the War Minister launched an assault on the temple, which resulted in a battle between the temple's inhabitants and the Fire Nation forces under War Minister Qin's command.
During the battle, these tanks easily overwhelmed the temple defenses, and advanced to the temple virtually unimpeded. However, before they could proceed to destroy the temple, Sokka and the mechanist ignited a natural gas pocket in a nearby crevice, causing a huge explosion that destroyed the tanks, along with much of the mountain, and forced the Fire Nation to retreat.
These tanks were also used in the Siege of the North, where several of them employed ballistae to destroy the walls of the Northern Water Tribe. However, they were destroyed by Aang and La, the Ocean Spirit, who worked as one to annihilate the entire Fire Nation naval fleet.
The tanks appeared again when War Minister Qin launched an attack on the Earth Kingdom capital overseen by Princess Azula, where he used the Fire Nation drill in an attempt to breach Ba Sing Se's Outer Wall. They either retreated or were demolished when Aang destroyed the drill.
These tanks later appeared during the Day of Black Sun, trying to defend the Fire Nation Capital from the invasion force. The tanks seen in this battle traveled on treads. Dozens of these tanks attacked but were of little use against the earthbending-powered tanks, which crushed these tanks upon contact. The tanks could not stop the invaders from reaching the capital, but the invasion was later repulsed by the Fire Nation airships.
Hundreds of tundra tanks were used to fight the Order of the White Lotus during the group's assault on Ba Sing Se. However, they proved no match for the masters of the Order and dozens were destroyed as the city was finally liberated. King Bumi stacked many of these tanks, which were later used for games by the city's citizens.
After the end of the Hundred Year War, the tundra tanks continued service as the primary military vehicle of the Fire Nation. When the Harmony Restoration Movement escalated into an open conflict between the Earth Kingdom and Fire Nation, Fire Lord Zuko employed a small but effective task force to defend Yu Dao from the Earth Kingdom Army. This task force also included seven tundra tanks. However, the tanks were disabled by Toph Beifong's metalbending before the battle began, forcing the tank crews to fight on foot.
Tundra tanks are heavily armored all-around vehicles with two types of wheels: wheels equipped with spikes and treaded wheels. The former are primarily used over icy terrain, thus in mountains or the poles. The latter are suitable for almost all other environments, including deserts, grasslands, and urban areas. The steam engines that power the tundra tanks are extremely efficient and durable engines; extreme climatic conditions cannot harm them, while they allow the tank to scale even sheer rock cliffs using the two grappling hooks on the front end. A particularly notable feature of the tank is the unique rotating cabin, capable of righting the tank should it get flipped over. This feature is particularly useful when combating earthbenders or airbenders. At the bottom of the tank is an escape hatch used when the vehicle sustains severe damage, and the operators must leave.
However, the unmodified tundra tanks are only able to fight infantry due to the lack of anti-tank or generally heavy weapons. Indeed, the primary weapon of the tank are fireballs and fire streams which are discharged out of four hatches on each side of the top of the cabin by the firebending crewmembers. Nevertheless, the firebending is lethal to infantry and cavalry, and can even knock heavy tanks on their sides or back after a series of stronger blasts. However, the tundra tank can be modified for heavier fighting by employing a ballista on its top. This metal ballista shoots heavy projectiles to destroy the walls of fortifications, but by its nature, can also successfully attack ships and heavy tanks.
Apparently the tank only requires a crew of two for its running, one firebender and one driver. However, as was the case in several battles, one or two additional engineers are often added to the crew to ensure an increased efficiency. The equipment and protective clothing of the crewmembers is dependent on their number. If the crew consists of two, both will wear heavy full body armor and helmets with faceplates, since the tank is less strong and therefore more vulnerable to attacks. If the tank is fully manned, the crew will wear light armor. Engineers always wear safety glasses.
These tanks have very few weaknesses to speak of. However, the counterbalancing system of the tanks work on water, enabling a waterbender to freeze the axles of the tank's wheels, causing them to fall off and rendering the tank immobile. Its design also enables metalbenders to easily destroy the tank by the removal of the screws. The tanks are apparently inferior to Earth Kingdom tanks, seeing as how they were only able to take down one during the invasion of the Fire Nation.
Bumi, a powerful earthbender, was able to both jam the fire portals and launch the tanks into the air, indicating that brute force might be the only way to deal with the tanks.