The Southern Raiders were a Fire Nation Navy special forces unit with the purpose of raiding the Southern Water Tribe when deemed necessary by the Fire Nation military, responsible for conducting savage attacks all over the South Pole and the Earth Kingdom. Their duty was to capture or kill Southern waterbenders to prevent hopes of resisting Fire Nation rule.
The Southern Raiders attacked the Southern Water Tribe several years before the Avatar was discovered in his iceberg; they were searching for a rumored last waterbender, who, unknown to them, was an eight-year-old girl, Katara. During said attack, their men created a diversion to attract the attention of the warriors, which allowed their commander, then Yon Rha, to interrogate Kya, the chief's wife, as to the waterbender's whereabouts. Kya lied and told him that she was the waterbender, protecting her daughter. The commander, unwilling to take her as a prisoner, killed her. This incident further deepened the Southern Water Tribe's hatred for the Fire Nation and prompted all of the warriors to leave the Tribe to help the Earth Kingdom win the War. It would also give Katara and Sokka the desire to help Avatar Aang once he awakened.
The Southern Raiders would eventually move their base to Whale Tail Island and appoint a new leader. They had a different helmet design than other Fire Nation soldiers, resembling a bird. The unit also possessed special ships that were smaller and faster than the traditional Fire Nation destroyers. The Raiders' warships were perfect for attacking coastal villages. Their smaller size and improved maneuverability allows the ships to pull up close to the shore and surprise the enemy.
The Southern Raiders were tracked down by Katara and Zuko in the final year of the War. They spotted the Southern Raiders' flagship near Whale Tail Island, after which Katara launched a vicious wave of attacks that left the Raiders defenseless. She then interrogated their leader, who she initially thought was Yon Rha until she realized that he was Yon Rha's replacement. However, the new commander was willing to tell Katara Yon Rha's location.