Author Tract: This fic is essentially the author's soapbox for complaining about what he sees as the Hetalia fandom's tendency to trivialize the atrocities of the Axis Powers in general Nazi Germany in particular during World War II.
Also, though the installments are written mostly in American English, the characters' voices follow anglicized grammatical structure of their own languages. Japan uses no contractions, Russia uses short sentences but long paragraphs, France always inflects upward, etc.
When Austria tells Messaien what he is, Messaien thinks he means to say that he is Austrian and says "Your French needs work." Austria clarifies: "No, I am the State".
Bittersweet Ending: Romano, aka. South Italy leaves his brother, with the implication that there will eventually be fragmentation and an Italian civil war. However, in doing so he "attains" Spain's respect and love.
Came Back Wrong: Word of God says four characters will die. Three already have, and the authors have left tracks stating that they, being Nations, are not gone for good. Greece has already been reincarnated, and Switzerland is a poltergeist. But as for France, well...
Chickification: Pulled on Hungary, a fearless Action Girl in canon... whom Prussia easily captures, then brutally tortures and rapes to "teach a lesson" to her beloved ex-husband Austria, whom Prussia is holding hostage..
Color-Coded for Your Convenience: The Fascists wear greyscale, the communists and socialists wear blood and gold.It is implied that civilian Nations wear colors, mostly those not associated with either side; when Austria is let out of his glass box, he wears first a red, then a blue scarf.
Driven to Suicide: At some point around the time England went mad, hundreds of citizens of the Empire and Commonwealth engaged in mass suicides, many hurling themselves off the White Cliffs of Dover. Those who couldn't get to the British Isles did the same thing in Calcutta. By 1949, several thousand have killed themselves.
For want of Japan, poor France was lost; For want of poor France, America was lost; For want of America, his mind was lost; For want of his mind, the Empire was lost; For want of the Empire, the war was won, Though not by the Nation who started it all.
Good People Have Good Sex: Subverted for America. In fact, this seems to be a running thing with the sexual relationships in AHEW. Prussia's among the worst of the lot and enjoys himself immensely, specially through raping the few AHEW-important women; England and Japan are happily malevolent together through the entire first half of the chronology, so much that France complains about how much time England spends having sex; and, well, the Drunken Fascist Orgy.
Grey and Gray Morality: Neither the Fascists nor the Communists are immune from atrocities, but neither is presented as completely monstrous. May be Black and Gray Morality if you give the Communists the benefit of the doubt.
Holy Roman Empire: The WHRR is an attempt at renewing this through the unification of the European continent.
I Have Your Ex-Husband: Prussia uses Austria to force Hungary to collaborate. And by "force", we mean he kidnaps, rapes and tortures her in front of Austria.
Jossed: Greece's in-story claim that Rome killed his mother Ancient Greece is actually incorrect by Hetalia canon standards, as the old CD dramas all but state that not only she outlived Rome via becoming the Byzantine Empire... but that Ottoman Turkey was the one who killed her.
Lyrical Dissonance: Fratelli d'Italia in "All The Rest Have Thirty One", Vesti la giubba in "Put on the Costume", "The Sun Whose Rays Are All Ablaze," and pretty much the entirety of "FULL STOP", or whenever England sings at all.
Mad Oracle: In the second half of the continuity England is either this or a Talkative Loon. The one thing that stands in the way of his being purely a Mad Oracle is that he can't see the future; he can see the story, because he can see all stories right now, and all of them are true.
During "The Seventh Door", Prussia and Hungary only speak in the rhythm of Bela Bartok's Duke Bluebeard's Castle: "Judith, tell me, will you follow?" "I will follow, Kekzakallu." The title of the installment also comes from that opera.
"City of Light" follows and uses Dreyer's Joan of Arc as a focal reference.
The Rashomon: So what happened during the German-Russian conflict on the (former) Polish border (or was it?) in September 1939? "The Left Hand Doesn't Know" and "What The Right Hand Is Doing" give us about four different accounts, and by the end of "What The Right Hand Is Doing," Russia still hasn't figured out what went on, or even what the Party line about what went on should be. Germany gives the situation as much resolution as it's going to get when he declares war on Russia, though.