Because he can't trust either of them to do it, and he tells them in exactly those words, Claude seizes control over the negotiations and the makeshift 'war table' they've made out of Edelgard's pauldrons, his sash, and Dimitri's gauntlets.
Claude tells them what Byleth spoke of while the two of them were quarreling and holds nothing back. There's anger in his voice, there's disappointment in them both, and he's feeling more than a little self-righteous in that moment. He lectures them from a leadership standpoint and then on a personal one for as long as he manages to hold the floor. There's no mistaking he's pissed at the two high-born nobles for their roles in this war, but he's just as angry and disgusted with himself as well for playing the same stupid game and perpetuating the exact thing the three of them want to eliminate.
He says exactly those words too.
It's harder than he initially thinks to keep his voice low enough so as not to disturb the woman sleeping behind them and it takes a few widened eyes from Edelgard and a dirty look from Dimitri before the volume control kicks in.
Whether it's Fate that brought them together like this, the Goddess Herself guiding them into one place, or just a wildly unlikely fluke that reunited them, Claude doesn't care. What happened to the three of them in the past, while it matters as far as the events that brought them to this point, doesn't matter in the present moment. He doesn't care and knows he's lying because he does care, who the bigger bastard is or who holds the lion's share of the blame in all of this.
What matters is that they have an opportunity they will never have again to settle it, once and for all, between the three of them and make something out of the mess they've all had a hand in creating.
Dimitri gets the first lecture and he really lets the blond would-be king have it in regards to his recklessness, how the bloodthirst makes him more of a danger than Edelgard's tyranny- full offense meant, he assures the woman opposite of Dimitri- to ally and enemy alike. How that same desire for revenge has alienated his potential allies and left him vulnerable to Cordelia's coup. How he's going to get himself killed and where the actual hell is that going to leave the people who still give two shits about him who've already lost their homes? What of those who gave their lives to ensure the future of the Kingdom, that he would have a chance at happiness and to live on their behalf?
He asks if Dimitri understands that he's spitting in the faces of all the dead who gave their lives for him so that he can create a new future where tragedies like Duscur didn't have to exist.
By the time he's through, the man is white with rage and shaking with the effort not to reach over and throttle him.
Edelgard is the one he turns on next and he doesn't hold back on her. While the Prime Minister and his branch of nobility are definitely the biggest bastards in all of this, she's absolutely to blame for perpetuating their war and for choosing the same path Dimitri has. He rails at her for her arrogance, for deciding that sacrificing herself and who in Fodlan's name knows how many people for revenge-turned-unification was the only option she had left to her, and reiterates Dimitri's last portion in regards to the people she's not taking into consideration and how they feel about her impending death. Claude's twice the asshole because he knows her father was alive when she took the crown and asks her if this is what her father and siblings would have wanted to see.
Dimitri's the one who catches her by the wrist before it connects with Claude's face.
Claude finishes his piece by looping himself in for doing the same fucking thing; he's no better than they are even if he isn't on the path of revenge the way they are and doesn't have their tragedies or traumas to back his motivations. He's still playing the same war games they are, moving people like they're game pieces on a board with no thought to their feelings or how they may perceive his actions. Like them, he's been trying to go about it all alone because of how he thinks something should be done and has a complete lack of trust for pretty much anyone else on that planet.
"Now that we have that out of the way," his voice is less furious but no less stern. "Here's how we're going to do this, your Highnesses; you're each going to get an opportunity to light the rest of us up the way I just set the example for. When we're all done verbally ripping each other to shreds, we're going to go to separate corners and we're going to stay there for an hour to think. Really think about what's been said by the others, and then we're going to reconvene and go from there."
"And do what exactly?" Edelgard asks.
"Either end the war or bare our necks for Teach." Claude says with a long, frustrated sigh. "And, since you tried to slap me, you get to go last on the lecturing."
Edelgard ignores the looks sent her way when, about twenty minutes into her time alone to think, she rises and goes over to sit in front of the Professor. They can stare all they'd like; where she does her thinking is none of their business or concern. She kneels down and watches her sleep. Studies the dark shadows under her eyes and the telltale crease of her brow present even while she sleeps. She reaches out, unable to control herself, and presses the pad of her thumb against the indentation to smooth it out.
Byleth is a sound sleeper when she's comfortable around others, and Edelgard is both grateful and touched by the level of trust her dear teacher has in her. In them after so long.
What if Dimitri had begged her uncle to allow her to stay? Had asked his father and Lord Rodrigue to intervene on her behalf? What if he'd begged her mother to allow her to stay even just a little longer? She'd have missed the cruelty done to her siblings, would have born the guilt and weight of their deaths the moment she heard of it. Would have missed much of the pain and torture that had been her life for the next several years.
She would have been there when the Tragedy of Duscur happened and would have been there alongside Dimitri, Sylvain, Ingrid, and Felix when their families and friends were slaughtered before their very eyes. Would have seen him protect and would have helped him protect Dedue and other innocents. He wouldn't have been alone, the sole survivor, it would have been both of them. Together.
His dagger and her own and they would have fought as hard as they could to protect what little their pitiful strength could have.
And Claude… what if… if they had met sooner? If she had reached out to him sooner during the beginning of their Academy days? He was an outsider, he had no known trail and she and Hubert had tried to trace his tracks for the last several years. He might have had insight, the way he hinted during his dressing down of them both tonight, a different perspective and would have been able to work with her to achieve what she so desired without as much blood being spilled. He could have kept her, and the rest of them, on their toes and made her so terribly angry she forgot herself. Could have made her laugh in spite of her serious nature.
They might have been good together.
Her hand is gentle against Byleth's forehead as she smooths the bright green hair out of her face. She rests her palm atop Byleth's head and just enjoys the moment of silent contact. She's anchoring herself using her beloved teacher as a physical touchstone as she wades through the 'what-ifs' and 'might-have-beens' to look for an answer she can bring to their silly, misshapen 'war table'. Right now, she has no answers: she has a multitude of fears, misgivings, and a lot of anger she has nowhere to direct but at herself and that isn't helping her find a solution.
What kind of person would she have been like had Byleth come into her life sooner? If she would have had her before her plans really started taking off and bearing results she couldn't find it in her to argue with? If Byleth had been there the entire time instead of showing up now after the last five years?
Would she still be on this bloody path?
Was it too late…?