The battle commences in the Royal Plaza.
"I already failed the world once at Ba Sing Se; I won't let myself fail again."
The day of the eclipse has arrived. The invasion party assembles, bringing back some old, familiar faces, and everyone prepares for the coming battle. Using submarines and tanks built by The Mechanist to infiltrate, the invasion is started: Aang heads to the capital to face Fire Lord Ozai, while the invasion force starts battling its way up the city docks and heads for the capital on foot, hoping to secure the defenses by the time the eclipse ends.
Tropes:
- Action Film, Quiet Drama Scene: Preparations for the invasion are interspersed with scenes of Zuko making his own preparations to leave.
- The scene of Aang's Now or Never Kiss is also a very memorable example.
- Because You Were Nice to Me: Ming, one of the Fire Nation soldiers on guard in the prison, brings Iroh extra food and treats him kindly. Because of this, he makes sure to tell her to take the afternoon off on the day he's planning to break out.
- Car Fu: Sokka steers a bomb-filled truck into a gate before jumping clear.
- Chekhov's Gun: The invasion party makes use of the eclipse knowledge, allowing them to gain the upper hand against the depowered Fire Nation troops.
- Continuity Cavalcade: The fighters Hakoda and Bato bring to the invasion include Haru and Tyro, Pipsqueak and The Duke, the Mechanist and Teo, the Hippo and the Boulder, and the Swamp Benders.
- Cup Holders: The snack compartment in Aang's glider. It turns out to be quite convenient.
- Disorganized Outline Speech: Sokka's attempt at briefing everyone on the invasion plan.
- Dramatic Irony: The audience has been privy to information since the end of Book Two that the Gaang and their allies didn't know — namely that Kuei accidentally blabbed the knowledge of the eclipse and the invasion plan to Azula when she, Mei, and Ty Lee were posing as Kyoshi Warriors. So the audience has known the Fire Nation has had that intel in the interim and the dramatic tension has been where and when the Gaang would finally realize their endgame had been compromised all along.
- Dynamic Entry: Aang bursts through the palace door shouting that the Avatar is back and ready to fight. He then finds the palace completely empty and thus the moment is wasted.
- Easily Forgiven: The Boulder and the Hippo are recruited for the invasion, despite the fact that they previously helped Xin Fu capture Toph and Aang, with the intention of offering the latter to the Fire Nation for the reward money.
- Group Hug: The team hugs before Aang leaves to face the Fire Lord.
- Heel–Face Turn: The Boulder and the Hippo have given up on trying to capture or fight Toph and are now fighting to protect their Kingdom.
- Hope Spot: Team Avatar finally uses the eclipse to their advantage and Aang heads over to face Ozai. Unfortunately, he finds the Fire Lord not around.
- Ice-Cream Koan:Huu: Pants are an illusion and so is death.
- Important Haircut: Before they leave for the invasion, Aang shaves his head to once again fully reveal his tattoo.
- It's Quiet… Too Quiet: Aang realizes that something is wrong when he reaches the royal capital and finds it completely deserted.
- Lock-and-Load Montage: Team Avatar all get suited up in their various wartime outfits, stock up on weapons and armor, and in Aang's case shaves his head and puts on his new Airbender robes. Inverted with Zuko, however, who takes off his armor and removes his topknot to signify his Heel–Face Turn.
- Magitek: The submarines and the tanks are propelled by bending and steered mechanically.
- Now or Never Kiss: Aang, realizing he might not return, kisses Katara just before he leaves, effectively revealing his feelings to her.
- Poor Communication Kills: While it's not explicitly pointed out, Kuei obviously failed to tell the Gaang that he'd discussed the invasion plan with the "Koyshi Warriors" back at the end of Book Two. Had he done so, they would've realized their plans had been compromised for months.
- Post-Kiss Catatonia: The above causes this for Katara.
- Rousing Speech: After Sokka fails miserably at this, his father Hakoda takes over and shows everyone how it's done.
- "Shut Up" Kiss: Aang's Now or Never Kiss with Katara is also one of these.
- Sibling Team: Sokka and Katara work flawlessly together to take down one of the guard towers during the siege.
- Skyward Scream: Courtesy of Aang when he finds the Royal Palace to be empty;Aang: Fire Lord Ozai.....WHERE ARE YOU?!?!
- Sneaky Departure: Zuko leaving to follow his call. He leaves behind a note for Mai.
- Special Guest: The female prison guard who shows sympathy to Iroh is voiced by tennis star Serena Williams. She was a huge fan of the show, and when the producers learned this, they offered her a small role.
- Unspoken Plan Guarantee: Played straight as an arrow. The part of the plan that Hakoda reveals to us fails but the part we don't hear (the sneaky submarines) works out perfectly.
- You Are Better Than You Think You Are: After Sokka is left dejected after he failed at his Rousing Speech and his father had to sub in for him Aang assures him that his moment to prove himself won't be by giving a speech; it'll be on the battlefield. Sure enough, Aang is right and Sokka proves himself by leading the charge after Hakoda is left injured.
- You Are in Command Now: Sokka takes charge of the invasion after his father gets hurt.
- Your Princess Is in Another Castle!: Aang charges into the throne room ready for his Final Battle against the Big Bad Evil Overlord... and he's not there. Ironically, the princess is in this castle, to delay our heroes until the eclipse is over (though we don’t get to see that until Part 2).
