Although highly incompetent, he was promoted to the rank of General. His poor commanding skills were countered by his eloquence, allowing General Sung to talk his way out of most problems, and leaving the real work to those who "knew what they were doing".
Sung encountered Team Avatar when he was defending the Outer Wall against the Fire Nation assault under the command of PrincessAzula. He smugly turned down AvatarAang's offer to help, believing to have the situation under control, as the Outer Wall had withstood many previous attack successfully, with the exception of GeneralIroh's, and proceeded to send in the Terra Team to hinder the giant drill. Watching his elite team of earthbenders succumb at the hands of Mai and Ty Lee, the general panicked and humbly requested Aang's assistance.
As the drill bore through the wall, General Sung commanded his soldiers to continually launch giant boulders down at the drill, despite being requested to refrain. This command initially impeded Aang's efforts in halting the drill's further progress, as he frequently needed to dodge the large projectiles. When Aang succeeded in piercing through the drill's metal shell, the machine exploded, sending thick slurry all over the place, reaching as high as the top of the wall, where it completely covered the general.
Sometime later, Sung and the other members of the Council of Five were captured by the Dai Li on the orders of Princess Azula to complete her coup against Earth KingKuei.