Fire Nation drill


 * This article is about the object. For the episode by a similar name, see The Drill.

"fire"

- This drill is a feat of scientific ingenuity and raw destructive power. Once it tunnels through the wall, our troops will storm their city. The Earth kingdom will finally fall, and you can claim Ba Sing Se in the name of your father. Nothing can stop us.

The Drill was a very large, hydraulic, metal drill which was designed solely to penetrate the "impenetrable" walls of Ba Sing Se, so that the Fire Nation could conquer the Earth Kingdom capital and ultimately win the War. The operation was overseen by Princess Azula at the Battle of the Drill; it was, however, a failure as Team Avatar intervened.

History
The drill was originally designed by The Mechanist at the Northern Air Temple. It is possible the Fire Nation forced him to design the drill, as he was forced to design and make new weapons for them under the threat of the destruction of his home. It took the Fire Nation laborers over two years to construct.

The drill was used in a major attack on Ba Sing Se, in an attempt to breach the city's Outer Wall. War Minister Qin and Princess Azula personally oversaw the attack, and the drill was escorted by multiple tanks. The drill was opposed by the Terra Team, an elite force of Earthbenders. They managed to knock away several tanks and attempted to slow the drill's advance before they were ambushed by Mai and Ty Lee. Before they had time to react, Ty Lee used her chi-blocking to disable the entire team, leaving the wall vulnerable.



Unfortunately for the Fire Nation, Aang and his group arrived at the city just as the drill launched the attack, and they immediately sought to destroy the vehicle. While Toph attempted to slow the drill down from the outside, Aang, Katara, and Sokka infiltrated the drill to destroy it from the inside. Using schematics they stole from an engineer, they discovered that the outer shell was sustained through the use of various support girders connected to the engine, so they proceeded to destroy them. Unfortunately, the drill made contact with the outer wall and actually succeeded in drilling a hole clear through the barrier, so the group doubled their efforts and only partially disconnected the girders so that the shell would collapse when Aang delivered the final blow.

Azula, Mai, and Ty Lee attempted to stop the gang from destroying the drill, with Ty Lee pursuing Sokka and Katara through the slurry while Azula faced off with Aang. Mai bailed out as the slurry disgusted her. Katara and Toph bended the slurry to shove it back into the drill along with Ty Lee, building up the pressure inside the shell. Azula tried to stop Aang, but he knocked her off the drill when he shoved an earthen wedge into the outer shell, causing the support beams to dislodge and the shell to collapse. The drill then exploded in an earthen mess when the slurry pipes burst, stopping the drill dead in its tracks. It was left jammed in the wall, blocking the Fire Nation's only route into Ba Sing Se.



The drill remains lodged in the outer wall. It was encased by a temporary wall of earth and the gang used it to prove to Earth King Kuei that the Dai Li had hidden the century-long war from him, earning his support for the proposed invasion of the Fire Nation.

It is unknown if the drill was eventually dismantled, or if it was indeed moved at all.

Design


The drill is larger than some villages, and is at least a mile or two in length. It is so big that it actually houses an entire brigade of Fire Nation engineers, who are needed to make repairs and clean out the pipelines. Several metal support beams connect the protective outer shell of the drill to its engine inside. As the drill digs into an earthen structure, the rock is chewed up and turned into slurry, a mixture of rock and water that is dispensed into pipes and dumped out of the rear of the drill.

Connection
The drill has a construction and function similar to a tunnel boring machine. The difference is that the tunnel boring machine is made not for war, but for building tunnels for traffic, often for trains. However, it can only drill through hard mountain, is very slow, and is expensive, but is much safer to use than building tunnels the traditional way, through the use of laborers.

The machine also bears a resemblance to the Ritter Midgard-Schlange - a 524 meter long Nazi war-machine devised for use in WWII, but which was never built - which main purpose was to breach enemy fortifications.

Trivia

 * It's unlikely that the drill would eject the slurry mix out the back of the machine. It's much more plausible that the system would be a closed loop, with the rock and earth being seperated from the water and lubricants for reuse. The drill would also have to carry an incredible amount of water to be able to expel it as shown.