Confrontation at Tu Zin

The Duel at Tu Zin was a small skirmish between Team Avatar, Zuko, Iroh, and Princess Azula of the Fire Nation as the latter attempted to capture or kill Avatar Aang after she and her friends Mai and Ty Lee successfully deprived the team of sleep. The duel occurred at an abandoned Earth Kingdom town of Tu Zin. Exiled Fire Nation nationals Prince Zuko and Iroh also arrived at the abandoned town, both to capture Aang as well as defeat Azula. The duel ended in a stalemate with the cornered Azula wounding Iroh before retreating.

Background
Azula was originally tasked by her father, Fire Lord Ozai, to apprehend exiled nationals Iroh and Prince Zuko after Iroh's treachery at the North Pole. Azula did find the two and pretended that she was to escort them home to be near the Fire Lord. However, Iroh suspected the lie and he and Zuko escaped from Azula. Not willing to alert them of her presence and being slowed down by the royal procession, Azula recruited Ty Lee and Mai to hunt down Zuko and Iroh. However at the captured city of Omashu where Mai's family moved to supervise the occupation, Azula's group encountered Team Avatar as they attempted to rescue King Bumi. Team Avatar also escaped but Azula now had an additional target to capture. After their escape, Team Avatar found Toph Bei Fong to teach Aang Earthbending. Meanwhile, after a quarrel, Zuko and Iroh went their separate ways. Zuko took refuge at a small Earth Kingdom village and befriended a young boy until the villagers discovered his true identity. Iroh decided to covertly track him.

Azula and her group followed Team Avatar in a transport following the trail of Appa's shed hair. Team Avatar noticed the transport and attempted to lose them, but Azula's group trailed them into the night, catching up before any real rest could be had, leaving Team Avatar sleep-deprived.

Duel
After the trio of girls had been following them and kept them from sleeping, Team Avatar was grouchy and on edge. After an argument with Katara, Toph temporarily left the group only to bump into Iroh and have a conversation with him, neither realizing just who they were talking to. After washing Appa to rid him of loose hair, the three remaining members of Team Avatar split up, hoping to divide their pursuers. Katara and Sokka flew on Appa in one direction while Aang used his glider to fly in the other with a bag of Appa's hair, using it to leave a trail. While he succeeded in drawing Azula's attention, she realized his plan and sent Mai and Ty Lee to fight the others.

While Katara and Sokka attempted to find Toph, Mai and Ty Lee caught up with them and began a small fight. Katara was able to dodge Ty Lee's Chi Blocking attacks but ended up pinned to a tree by Mai's daggers, unable to waterbend. Ty Lee had better luck with Sokka and he was virtually paralyzed by her. The fight ended when Appa air-slammed Mai and Ty Lee into the river, allowing Katara and Sokka to escape.

Having exhausted the bundle of Appa's hair and too tired to run any further, Aang waited for his pursuer to catch up in the abandoned village of Tu Zin. As Azula arrived and prepared to confront Aang, Zuko intervened between them, dividing Azula's attention from the Avatar. The three began a lengthy fight, though most of the time Zuko and Aang were fighting Azula, occasionally sparring with each other when she was momentarily out. Azula managed to knock out Zuko, and just before she could deliver a final blow against a helpless Aang, Katara, Sokka, and the reunited Toph arrived, outnumbering Azula. Zuko woke up to see Iroh standing above him. All six then ganged up on Azula and cornered her. She pretended to surrender, but took advantage of Iroh's momentary distraction of finding his new-found friend, Toph, to wound him with blue fire in his chest. All four benders struck back at Azula in retaliation, creating a huge explosion. Under cover of the smoke, dust, and steam, Azula mysteriously escaped and a distraught Zuko forced Team Avatar to leave without letting them help the wounded Iroh.

Aftermath
Afterwards, Team Avatar found a location to sleep safely, while Zuko took care of Iroh. Sometime after, Aang prepared to learn Earthbending, while Iroh, partially healed, taught Zuko how to redirect lightning in case Zuko faced Azula again.

The duel was not the first time, or the last, in which Zuko and Iroh unofficially teamed up with Team Avatar against a common foe.