He knows.
Gilbert knows how the others went— he wasn't there to see Augustus, but he knows it was just like Ewald, just like Aretaunin, just like Herannuen and—
—well, not Heinrich. Poor Heinrich.
But the point is he knows how nations go when they've collapsed. He would, he's Prussia, he's collapsed a fair few himself in his time, and his time is past now and Ludwig operates better in this new world of paper wars than Gilbert ever could. It's honestly about time Gilbert struck camp and moved on.
But that's the thing. Ludwig. He's still a kid (just like Heinrich was, maybe a lot stronger and healthier and bigger but somewhere under the bureaucracy and education he's the bloodstained, terrified child on the field at Austerlitz), honestly just a kid, and Gilbert has to keep an eye on him. Make sure he doesn't spend all his time pushing pens and fretting about the Euro. No telling what would happen to him otherwise without Gilbert there to look out for him.
And while he's looking out for people, there's Francis and Antonio, what would they do without him? The Bad Friends Duo just does not have the same ring, and you need three people to properly annoy Roderich. And what would Alfred do? Gilbert taught him everything about warfare, helped him with his Arthur issues, and game night with only Kiku can't be as fun as game night with Kiku and Gilbert.
Gilbert knows he's not really necessary to the world anymore, and that hurts, but it's true— nobody in Europe wants any more wars, Germany ticks along quite well with Ludwig in charge, there's no way to stick it to Roderich quite the same way Gilbert could have before, and Ludwig has friends now, people he can eat lunch with, a squeeze of his own (and Gilbert is not jealous about that, nosirree)— he'd live if Gilbert moved on.
He's not necessary. And he's tired, so tired sometimes, is this how all old empires feel? Do Arthur and Roderich and Francis and Antonio creak and drag through some days, phantom pains of Danzig—Gdansk—Danzig and Walls and centuries of warfare from Jerusalem to Paris, when their glory days are gone so far away they're something for children to pretend to do their homework on, when nobody but him remembers the Battle of Hohenfriedburg?
Gilbert could go.
He could.
But, he thinks, watching Ludwig with Feliciano, un-tuning Roderich's piano, finally beating Kiku on Rainbow Road, Gilbert never did know when to quit.
drabble drabble
Augustus is Rome, Ewald is Germania, Aretaunin is Mama Iberia, Herannuen is Mama Gaul (the name is dark-ages Breton, which was the closest I could get to ancient Celtic in France), and Heinrich is the HRE.
Austerlitz was the battle (read: resounding ass-whooping of Austria by France) that resulted in the dissolution of Holy Rome.
Prussian generals were responsible for most of the military training of the Continental Army in the Revolutionary War (see: von Steuben)
Danzig/Gdansk is a port in what is now Poland, which was hacked out of Prussia and handed to Poland, along with the rest of the Polish Corridor, by the Treaty of Versailles.
From Jerusalem to Paris: the Teutonic Knights were Crusaders, and the Prussian army invaded France on multiple occasions.
The Battle of Hohenfriedburg is considered one of the crowning achievements of Friedrich the Great, when he whooped the Austrians during the War of Austrian Succession.