"No, it's been separated from the pack. I understand that pain. It's how I felt when the Water Tribe warriors had to leave me behind. They were my family, and being apart from them was more painful than my wounds."
— Bato to Sokka and Katara about a wolf.
Bato was a member of the Southern Water Tribe and a close friend of Katara and Sokka's father, Hakoda, since childhood. He was somewhat of a paternal figure to Katara and Sokka in their father's stead, thus he cared about their well-being and was a loyal and brave warrior who would do anything to protect his tribe.
Bato was born and raised in the Southern Water Tribe, and he was good friends with Hakoda. The two of them often played pranks on other members of the tribe and enjoyed spending time together.
Bato left the Southern Water Tribe around 97 AG, along with the other men of soldiering age. Some time after, Bato was badly burned by a Fire Nation soldier, and brought to the abbey, where the sisters took care of him and nursed him back to health.
During their travels, Aang, Katara, and Sokka found Bato's ship on a beach. Once Bato found them camping near the vessel, Katara and Sokka were elated to be around him, feeling almost at home again in his presence and his tent, which was decorated with furnishings from the South Pole. Bato was Hakoda's best friend as a child and through him, Sokka and Katara felt a connection to their father that they had not had in years. The three talked and reminisced long into the night, leaving out Aang. Bato acted as somewhat of a surrogate father toward Sokka and agreed to take him ice dodging, since Sokka never had the chance to with his own father. He also bore news of their father, stating that he awaited instructions on how to relocate him and the other Water Tribe men and offered to at least send word to the two of Hakoda's location as they accompanied Aang. However, in the comfort of their reunion, Katara and Sokka began to lose sight of where they were truly needed, as Aang began to feel betrayed and alone. Although at one point Sokka and Katara opted to accompany Bato on a journey to reunite with Hakoda, the siblings soon realized their duties to Aang and parted with the tribe member.
In the spring of 100 AG, Sokka and Katara received a message telling them that their father was at Chameleon Bay. Sokka agreed to reunite with his father while Katara stayed behind with the Earth King. When he reached Chameleon Bay, he walked into his father's tent, where a war meeting was in session. Bato, sitting next to Hakoda, tapped him to signal that Sokka was in the room. Later, Bato filled tangle mines and made mention of Hakoda's dry sense of humor as well as Sokka's similarity to his father.
That summer, Bato was a part of the invasion force which intended to attack the Fire Nation Capital on the Day of Black Sun. He was one of the many warriors to land on the Fire Nation Capital beach, and proved to be a good leader during the attack. When Hakoda was unable to guide the invasion force, Bato took over his position of leadership, seemingly becoming the new commander of the soldiers. When Aang failed to defeat Fire LordOzai, the younger soldiers were told to escape on Appa while the adults surrendered, Bato among them. Hakoda later stated that Bato and the remainder of the invasion force were sent to the Capital City Prison.
Bato was freed from prison following the Hundred Year War's end, and he joined his friends and allies at the coronation of Fire Lord Zuko at the Fire Nation Capital.
The pronunciation of Bato is similar to bateau, the French word for "boat". Seeing as he is the one that initiates Sokka to ice dodging using his boat, it is an appropriate name. It should also be noted that "Bato" is an anagram for "Boat".
When Bato first encountered Sokka at the abbey, he was recovering from a battle and had the majority of his torso and left arm bandaged. When he met him again some time later at Chameleon Bay, Bato had recovered. His bandages were removed, however, his skin was still marred red from the burns. By the time of the Invasion of the Fire Nation capital, his arm was perfectly healed.
To curb his homesickness, Bato decorated his quarters at the abbey in a fashion that would remind him of his own igloo at the South Pole.
Bato was the tallest of the Southern Water Tribe warriors seen.
Bato's armor was the only Water Tribe member's who had a distinct symbol painted on his helmet.