Iroh remembers listening to his grandfather's tales of the war.
Iroh couldn't remember not knowing his grandfather's story. In some ways, it was the story of the Fire Nation of grandfather's generation: a nation that had been raised by conquerers to be conquerers or else, who turned their backs on that past and became something better, something more just. There were still factions who embraced the old ways, who took Great-Grandfather Ozai and Great-Aunt Azula as martyrs, who had looked on the nascent Equalist movement as a result of the current Royal Family's weakness. But most people had instead embraced the ideal of peace, of harmony between the elements, of a military that did more work protecting merchants from pirates than against another nation.
Military tactics had changed since his grandfather's day, but slowly. Ships were more efficient, and had space for earth and waterbenders. Tanks benefited from the developments that made satomobiles into things a family could afford, but they were still tanks. Even airships - which weren't adopted until late in the war - were the same basic design. The old Fire Nation had used them as troop transports, and as platforms for aerial firebenders, but gas bags were fragile and combustable, and the airships maneuvered like a drunken sky bison. Unlike Sato's powered gliders.
Those had caught them all by surprise, and Iroh knew that they would change things. What he didn't know was how. He studied the plans that they'd found, not quite making sense of how they worked. He'd gained a basic understanding by having to fight them, but that had been by necessity. He could ask Asami Sato for assistance: they were hers now, but he didn't know if the old man's mechanical genius had been passed to his daughter along with her truly remarkable driving skills.
He'd looked out the window, catching a flash of red as Tenzin's daughters played with their own airbending gliders. Those Iroh understood: they were just kites, augmented by bending. You could even build a glider that could be flown by someone without airbending; the Northern Air Temple designed those, and Iroh suspected some of the Air Acolytes here had their own. He could even imagine using one with his firebending, though it would be a wild ride. Not unlike some of the desperate attempts he'd done to retake the city. "Are they really just kites with engines?" It couldn't be that simple. But it really was: the engine gave enough lift to fly, and the genius was in making an engine light enough that it could lift itself.
Tenzin interrupted him. "I hope you aren't thinking of building those… those things." He gestured at the documents.
"You'll have to ask Miss Sato about that, I'm afraid," Iroh replied. "They're her machines now. I'm honestly surprised the northerners didn't think of these first." He made a note in the margins to talk to the diplomats, see if Hiroshi Sato had visited up there. Or if any designs were missing. "They'll be able to figure it out now that they know it's possible."
"I don't mind if they do," Tenzin said. "They won't use them to chase down my family." He sighed. "Not that I think Asami would, either, but… you're right. Others will try to build these. I only hope that this has sated everyone's thirst for blood."
Iroh nodded. "And, now that people aren't trying to invade the city, I'm sure Miss Sato is already thinking of what other things people might use a powered glider for, so she can sell them." He certainly was, though he wouldn't tell Tenzin that.