Avatar: The Last Airbender/Recap/Book 1/19 The Siege of the North Part 1

""It's the Fire Nation. They've closed in on the North Pole.""

In the Northern Water Tribe, things are going great for our heroes. Aang and Katara are advancing quickly in their water bending lessons, and Sokka's friendship with Yue grows, even though he knows he can't have more. That all changes when they discover the Fire Nation Navy advancing with hundreds of ships.

With no other choice, the Water Tribe is forced to go to war; Aang attempts to attack the ships head on, while Sokka volunteers for a guerrilla mission, facing both death and Yue's jerk fiance Hahn. In the Fire Nation camp, Zuko hides in a disguise, before going solo into the Water Tribe in an attempt to kidnap Aang. Zhao, meanwhile, alludes to a secret plan of his own: to kill the Moon Spirit, the source of all Waterbending.

The reason Zhao can do this at the North Pole is that here, in the Spirit Oasis, the Northern Water Tribe's inner sanctum, live Tui and La, the spirits of the Moon and Ocean respectively. They inhabit the bodies of two koi, circling endlessly in the oasis' pool. Aang, his battle against the fleet fruitless, comes here to meditate, hoping to bring the spirits in on his side; Katara stays to defend him while Sokka and Yue oversee the defenses. It is here that Zuko finds him, and though Katara puts up one hell of a defense, Zuko defeats her and kidnaps Aang. This has the side effect of stranding Aang in the Spirit World, as his body is not where he left it. The episode ends with the walls of the city breached and Zuko toting Aang across the frozen tundra.

Tropes:
"Pakku: A couple years and you might be ready to fight a sea sponge."
 * Answer Cut: When Arnook says "It is with great sadness I call my family here before me, knowing well that some of these faces are about to vanish from our tribe," the camera flashes to.
 * Call Back: Some of the waterbenders stop a Fire Nation ship like the one seen in "The Boy in the Iceberg".
 * City of Canals: The Northern Water Tribe's city.
 * Instant Armor: Aang does this with snow as a joke.
 * My Name Is Not Durwood: Hahn can't get anyone's names right.
 * The Native Rival: Hahn, to Sokka.
 * One-Man Army: Averted. Despite being possibly the most powerful bender in the world, Aang can't single-handedly take on a whole navy.
 * Phlebotinum Battery/Field Power Effect: "You rise with the moon. I rise with the sun."
 * The Siege
 * Snow Means Death: Black snow, to be precise.
 * Take That: Confirmed by Word of God.