Battle of the drill

The Battle of the Drill was fought outside the Outer Wall of Ba Sing Se during the War. The Fire Nation assaulted Ba Sing Se using a drill, a massive device solely intended to drill a path through the city's massive walls to allow a larger invasion force to enter and take the Earth Kingdom capital. The drill was destroyed, and the Fire Nation was defeated, due to the intervention of Team Avatar.

History
Since the beginning of the War, the Fire Nation had searched for a way to conquer the famous Earth Kingdom city; however all previous attempts had failed. The country hoped that, by conquering the city, the Earth Kingdom would be severely crippled once the Council of Five and the Earth King were taken out of power, and therefore also conquering the last safe place for refugees misplaced by the War. Late in the War, the Fire Nation had been forcing a refugee and Earth Kingdom Mechanist to make weapons to aide them in battles, including the drill.

The Mechanist successfully designed the drill, a gigantic mechanism that was nearly impossible to beat and could breech the walls of Ba Sing Se with ease. The Fire Nation hoped that by breaching the walls, they would be able to set a path for their army to advance and finally conquer the city.

Battle
After completion, the drill and a small force of Fire Nation tanks headed towards the great city to break in. Unfortunately for the Fire Nation, the force arrived at the exact time as Team Avatar and Aang spotted the device.

Ba Sing Se's army was unprepared due to never having fought a major battle in years and their only means of defense were throwing boulders at the drill, which had little success. General Sung, who commanded the troops on the Outer Wall, did not see the drill as a real threat and was confident that the Terra Team, a group of elite Earthbenders would stop the colossal machine. Despite their best efforts, they were no match for Ty Lee and Mai, who promptly ambushed the soldiers. Ty Lee's chi blocking knocked out the entire team within mere moments. With the Terra Team helpless, Sung panicked and pleaded with Team Avatar for help despite his earlier thoughts of not needing it at all.



Team Avatar came up with a plan of hitting the drill's pressure points as Ty Lee had done to defeat the Terra Team. Aang, Katara and Sokka broke into the drill when Toph tried to slow it down from the outside because she could not bend metal at this point in time, and thus not 'see' inside the drill. Having stolen a schematic from a drill worker, the group headed for the front-most part of the drill where massive metal braces held the entire mechanism together. Aang and Katara began cutting completely through the braces using Waterbending, but found it was too much work to be done before the drill broke through the wall. Sokka suggested that they didn't need to cut through the braces completely, just halfway through would be sufficient, and that Aang could deliver a final blow that would destroy the weakened braces. Meanwhile, the crew found the drill worker that Katara had frozen earlier, prompting Azula to investigate the situation along with Mai and Ty Lee. The gang fled as they could not fight and cut through the braces at the same time.



Aang eventually separated from Sokka and Katara to deliver the final blow on top of the drill. Katara and Sokka managed to escape the machine from riding the slurry (a mixture of water and earth used to deposit the rock from the wall). Ty Lee followed them in the pipe, but Mai did not, stating "[Azula] can shoot all the lightning she wants at me; I'm not going in that wall sludge juice." Because the slurry was water and earth combined, both Katara and Toph were able to bend it from the outside and build up more pressure for when the blow was delivered. Ty Lee became trapped in the slurry since she had not given up pursuit.

Meanwhile, Aang dodged falling boulders from Sung's men as Sung thought that this would be an effective measure, even though it clearly wasn't. He also fended off Azula as he cut a hole into the metal exterior using Waterbending. Initially, Azula maintained the upper hand, dodging all of Aang's attacks, be it Earthbending, Waterbending, or Airbending. Eventually, she launched a massive Firebending blast that knocked Aang unconscious. As she prepared to deliver the killing blow, Aang recovered and fought her off with Earthbending. After removing her from the fight, Aang continued with the destruction of the drill. Aang used a rock to his advantage and made a wedge shape that he shoved into the front of the drill. He then used Airbending to speed-run down the outer wall, gaining momentum for the final blow. Azula launched a last-ditch attack to save the drill, but this failed and Aang landed on the wedge with huge force, sending Azula flying off the drill.



Aang's powerful attack caused the weakened braces to break apart simultaneously, causing the drill to collapse into a slurry mess, its pipelines exploding as the vehicle caved in, causing the entire area to be flooded in slurry, and it buried a large number of the Fire Nation troops escorting the vehicle or working within. Ty Lee was ejected from the slurry system but was largely unharmed. Azula also managed to escape injury. In the wreckage, a pristine and nonchalant Mai humbly said, "We lost."

Aftermath


The Battle of the Drill was a victory for the Earth Kingdom and once again stopped the Fire Nation from penetrating the Outer Wall. They were forced to return to the shores to await another opportunity to strike. Unfortunately, this victory was short-lived, as Azula would return to conquer Ba Sing Se several weeks later.

The drill wreckage was not immediately disposed of, though some ramps could later be seen, presumably as part of a clean-up effort; however, this proved to be a major asset for Team Avatar.

At least a month later, the gang used the drill as proof of the War to Earth King Kuei, who had been kept unaware of the War by the power-hungry cultural enforcers of the city, the Dai Li. Their leader, Long Feng, tried to convince the king that it was "a construction project", but the king was not convinced because the drill had the Fire Nation insignia on it, resulting in Long Feng's arrest. Kuei subsequently began to take more decisive action against the Fire Nation in the days prior to the city's capture.

Trivia

 * Metalbending is mentioned for the first time in this episode. It will later make its appearance in "The Guru".
 * The video game, Avatar: The Last Airbender - The Burning Earth, doesn't follow canon for this episode, as the bosses are Zuko and Azula against Aang and Katara. The battle is on a metal platform.

Non-canon

 * Avatar: The Last Airbender - The Burning Earth