Many months before the battle, Avatar Aang and his sky bison, Appa, were awoken by Sokka and Katara of the Southern Water Tribe from one hundred years of sleep within an iceberg. After learning that Aang was the Avatar and telling him of the Hundred Year War waged by the Fire Nation, the four befriended one another and decided to travel to the Northern Water Tribe together to find Aang a waterbending master. As the Avatar, Aang had a duty to master the four elements, put an end to the Fire Nation invasion, and restore peace to the world. After several months of traveling and evading Fire Nation pursuers across the Earth Kingdom, Aang and his friends reached the Northern Water Tribe where he and Katara began instruction in advanced waterbending.