Tundra tank

Fire Nation Tanks are large armored vehicles manufactured by the Fire Nation. They are first introduced in "The Northern Air Temple".

Overview
The Fire Nation Tanks are employed by the Fire Nation Army in their battles against the Water Tribes and the Earth Kingdom. These fearsome vehicles are crewed by at least three or four Firebenders, of which one fires projectiles from the tank's open-hatch canopy while the others drive the vehicle. These tanks travel either on treads or four spiked wheels, and are fairly fast for their weight and size. These tanks possess armor that is virtually impenetrable when engaged with conventional means.

Another trait to these tanks are their unusual number of surprises. If one of these tanks is flipped upside down, the crew compartment rotates upward, allowing the crew to continue their assault. Also, these tanks are perfect for climbing cliffs as they employ grapples on long chains that allow them to scale walls, and if these lines are destroyed and the tank falls off the cliff, a second grapple grabs the cliff and the tank continues climbing. These tanks are perfect for assaulting enemy fortifications and overrunning their defenses.

Weaknesses
These tanks have very few weaknesses to speak of. However, it has been demonstrated by Katara in battle that if Waterbending is used to freeze the axles of the tank's wheels, they can fall off, rendering them immobile.

History
It is unknown when these vehicles entered production, but they were first introduced in "The Northern Air Temple". They were likely designed by War Minister Qin and his unwilling accomplice, the Mechanist, an Earth Kingdom inventor. 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. 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 the Battle of the Northern Air Temple.

During the battle these tanks easily overwhelmed the temple defenses and advanced on the temple virtually undaunted. However, before they could proceed to destroy the temple, Sokka and the Mechanist ignited a natural gas pocket in a nearby crevasse, causing a huge explosion that destroyed the tanks and forced the Fire Nation to retreat.

These tanks were also used in the Siege of the North, where several of them employed ballistas to destroy the walls of the Northern Water Tribe Capital. However, they were destroyed when Aang and the Ocean Spirit merged to annihilate the entire Fire Nation invasion force.

The tanks again appeared when War Minister Qin and Princess Azula attempted to use the Fire Nation Drill to breach Ba Sing Se's Outer Wall in an attempt to invade the city. They were either destroyed or retreated when Aang destroyed the Drill. Hundreds of these tanks were used to storm Ba Sing Se when Azula conquered the city several weeks later.

Finally, these tanks appeared on the Day of Black Sun trying to defend the Fire Nation Capital from the invasion force later. The tanks seen in this battle traveled on treads. Dozens of these tanks attacked, but they were little use against the Earth Kingdom Tanks, which actually crushed these tanks. The tanks could not stop the invaders from reaching the Capital, but they were later repulsed by the Fire Nation Airships.

These tanks will likely reappear in future episodes.