Ozai is untested. He is a fierce warrior and a prodigious firebender, but the man has no real battle experience. He orders his team of so-called Special Ops down into a valley, giving Piandao the high ground.
Piandao watches from a high cliff while Ozai shoots lightning and spits fire. "Face me, Piandao! Prove to me you have fire in your heart, in your belly!"
Piandao lives on a steady diet of fire flakes and booze and meat covered in hot sauce. As much as he wants to stay and watch the spectacle that is Ozai, the fire in his belly is making its way through his system. He needs to take a flaming shit. He doubts that's what Ozai meant when he demanded to see the fire in Piandao's belly.
Ozai orders his men to find Piandao but when they finally reach the spot where Piandao had been watching them, he's long gone. The only evidence that he was ever there are his footprints and a letter, masterfully written, addressed to Ozai that reads "Maybe you should go back to trying to capture the Avatar and leave my capture in someone else's capable hands."
Piandao hopes his letter sends Ozai into a blind rage. People are stupid when they're angry. He waits...
Three months later, the Dragon himself comes to Piandao disguised as a friend.
"I'm planning a siege," the Dragon tells the Master. "Ba Sing Se..."
The words roll off Iroh's tongue like sweet music as if this were the first time anyone had sang that old song. "You have three successful sieges under your belt. I could really use your help."
Piandao blinks back at him.
"I'd love to hear your thoughts on the matter," Iroh says.
"I'm just trying to figure out which would be more tedious. A long boring siege that will probably drag on for years? Or watching the ink dry on my latest masterpiece?"
Piandao points to a sheet of paper tacked to the wall in back of Iroh. It reads "Go fuck yourself!" in what is perhaps the finest calligraphy Iroh has ever seen.
"What lovely penmanship," Iroh praises.
Piandao smiles. "Thanks."