"OD-AH-VIING!" rang through the air. Almost instantaneously, both sides stopped fighting, lay down arms, and slowly began to spontaneously retreat. Within minutes, there was a large, nearly circular empty space around Dovahkiin and dragon.
"Heh. Wimps," Odahviing snorted before preening. The Dragonborn checked. Yes, Odahviing was preening.
Someone cleared his throat, and the Dragonborn turned. General Tullius, Ulfric Stormcloak, and the associated Jarls of Skyrim stood a safe thirty or forty feet away, looking nervous.
"We surrender!" Ulfric shouted.
"Please don't summon any more dragons in the city!" Balgruuf cried, waving his hand at the bright, burning city behind him.
"Let there be peace!" Tullius agreed. The Jarls shouted agreement at him.
The Dragonborn turned to Odahviing. "You know, if I'd known summoning you would have this kind of impact, I would have done it long ago."
Odahviing was making repetitive hacking, growling sounds the Dragonborn was pretty sure was laughter. "This is great fun. Better than the time Paarthurnax drank an entire lakeful's worth of mead. Remind me to tell you that story some time. Paarthurnax must never live it down."
The Dragonborn nodded in bemused response to Odahviing's comment, which the assembled leaders of Skyrim took as an assent.
"Wait," one of the Jarls spoke up. "We still need a common enemy to whale upon while everyone gets used to the idea of not fighting each other again."
At that point, a Thalmor agent showed up and probably would have assassinated someone had he not had the bad luck to show up in the presence of several armies, the best fighters in the land of physical dominance, a dragon, and the Dragonborn.
"Problem solved," Ulfric said as he looted the body.
"Problem solved," General Tullius agreed, looking down at the now looted body while secretly stashing a spare set of boots under his cloak. "Now I just have to inform my Emperor."
And thus, the Empire made peace in Skyrim, threw out the Thalmor within its borders, and started up Empire VS Aldmeri Dominion: Round Two, also known as The Second Great War (or The Great War, Part II, after a minor interlude, depending on which historian you ask).