"Battle doesn't need a purpose; the battle is its own purpose. You don't ask why a plague spreads or a field burns. Don't ask why I fight."
Tvtopes associates Prussia with the trope Blood Knight and that in combination with a kink meme request is where this came from...
Russia had dragged off Prussia to execute him, with the blessing of the other allies, yet here Prussia is, handcuffed and a bit beaten up but alive in Moscow. Russia and his boss fight over him, almost getting physical. Prussia would be amused of it wasn't for the creepy way Stalin looks at him and he is worried about what they will do to him before they kill him. He is ready to die, if they put him in front of a firing squad he can take it, he wouldn't break down. But considering how they hate Germany and his boss they most likely plan to take it out of him instead. Prussia knows very well about the Red Army's brutality. They might keep him alive for years before they tire of him.
Stalin ultimately wins the fight by flattering Russia into submission. A good choice considering how it would be almost impossible for a human to win in a physical fight against a nation. Prussia is brought to a cell where he to his surprise isn't tortured, starved or anything else. Just bored.
Russia comes by every now and then to look at him with an unreadable expression. Prussia yells at him but Russia just smiles distantly, calling him his caged bird and disappears again.
It's Russia's boss who wants to talk and that is against all unwritten rules. Nation deal with each other without the involvement of bosses.
"Tell me about your brother," Stalin says.
"I'm not telling you anything about him," Prussia says. He's not going to give Russia and his boss ammunition to use against his brother. "You have to torture me first."
"I told you, I am not planning to hurt you. Tell me something else then."
"Is this some kind of Scheherazade thing where you keep me alive as long as I'm entertaining?"
But in the end Prussia is bored and loves attention. He talks about how he helped America train before the revolution and the disjointed story of how he fought off France, Austria and Russia, all at once. Prussia begins to suspect that Stalin is a little bit in love with the myth of the Prussian militarism and awesomeness.
"Why haven't I faded?" Prussia wonders at one of Russia's rare visits. Stalin stays at a comfortable distance at the other side of the bars but Russia gets close, touches him and his things and it makes Prussia really nervous.
"As long as someone remembers Prussia you will not fade, don't worry, countries almost never fade. But let us say I would for example, say shot you," Russia says. For emphasis he takes a gun from his coat and presses the barrel against Prussia's temple. "Then you would not recover because you are not immortal anymore."
"I-I think I get the point."
Russia caresses Prussia's face with the gun before he puts it away. Prussia dares to breathe again.
"I think we should have done that," Russia continues. "But my boss has such an disturbing crush on you."
"Hey, your boss understands the awesomeness that is Prussia."
"You are nothing anymore," Russia says. "How awesome could it have been?"
Russia refuses to give Prussia anything but the guards have apparently been told to give him what he asks for unless it has sharp edges. Prussia is frustrated and lonely but overall it could have been so much worse.
"Do you really want to be trapped here forever?" Stalin asks him.
"No, I want to go home and if you let me out I would."
"Everyone wants you dead and if they found out you were alive they would finish you off."
"My brother would help me."
"I wouldn't count on that. But fine, let us assume that your brother is willing to help you. Do you truly think he could? America wants you dead and your brother does not have the power to oppose him. I do."
Prussia stares at Russia's boss and hates him a little bit for being right.
"So I'm stuck here forever no matter what I think about it."
"You can help us instead. It is a shame for someone like you to waste away in a cell."
"I'm not going to help you fight my brother."
"Germany is yesterday's news. Why would I want to hurt him?"
Prussia knows Stalin is lying about that part, both he and Russia hate Germany.
"America is the enemy now, the one who wanted to dissolve you and control everything he has no business poking his nose into."
That on the other hand sounds reasonable.
"What do you expect me to do about that?"
"Help train our troops. That is what you used to do."
"I can do that," Prussia agrees and wonders what he is getting himself into. "But I'm not hurting Germany. The rest of the world... Well, I don't really care."
"Do you have a preference for a name I can actually write down on official papers?" Stalin asks.
"My human name is Gilbert, go with that."
"You have human names? Russia never told me that."
"Russia's name is Ivan," Prussia says and hopes it will annoy Russia to be called that by his boss. "Ivan Braginski."
Prussia gets put in charge of training up special forces that possess a great tolerance for weirdness. He is amazed by the level of trust that Stalin put in him. What if he was to run off and steal much weapons as he can carry? He doesn't, the truth is that he's nowhere to run. Being a fugitive nation in a world that doesn't want him seems like a much worse faith than to be a Russian officer.
It actually isn't half bad being Gilbert instead of Prussia for a while. Even if his new guys are Russians they are soldiers first and Prussia loves to be back in the game. They call him albino freak behind is back in the beginning, until he proves that his methods work and his skills are unmatched. Everyone knows 'Gilbert' has a special position and a mysterious past. The stories about his background are endless and become more and more insane. The latest one he heard is about Gilbert the turncoat nazi-vampire. Prussia loves it and dresses in black for an entire week to give it more credibility. He even puts on his iron cross again, beneath his shirt so it can be glimpsed every now and then.
"Is that really yours?" one of his soldiers eventually asks him.
"Who knows?" Prussia says. "Perhaps I took it from a fallen enemy as a trophy."
"No," the Russian says. "I don't believe that, not the way you handle it."
"I was a Teutonic knight," Prussia says. "Nazi bastards stole our symbols."
His Russian companion rolls his eyes and wonders if there is a difference. But the rumor about Gilbert the fallen Teutonic Knight cursed with immortality gains some popularity.
They try to force him to be East Germany but Prussia refuses, no matter how good it would feel to be a real nation again.
"I'm not going to hurt my brother," Prussia says. "That was my only condition."
Surprisingly Russia supports him.
"Do you hate me less now?" Prussia wonders when they are alone.
"No," Russia says. "Remember that my boss is mortal. I want you close when his time is over."