This fic is sad, happy, and a whirlwind of emotion. It's an AU, but handled well, with the history and the realism being well woven into the plotlines. The main focus is on Arthur and Alfred, though Francis and Matthew show up as well. Currently has a companion fic called Auf Wiedersehen, Sweetheart
, which is about the story of Ludwig and Feliciano in this universe, who are often mentioned, and though they never show up directly, they are still a pretty hefty part of the story. And more fics in the same 'verse are upcoming.