SPOILERS FOR EPISODE 22 of the anime.
Episode 22 broke my heart. But surely Dieter would have realised at some point that Levi was lying?
I made up Ernst's name, because Dieter's friend isn't named as far as I know.
Insignia
Dieter slumps in the wagon, oblivious to the hostile murmurings from the crowd. He can hardly bear to look at the Survey Corps insignia clutched in his left hand, but its presence gives him a kind of comfort nonetheless.
"This proves that they were alive," Captain Levi had said, and Dieter clings to those words as much as to the badge, because it's not only Ivan he's mourning now. If he hadn't spoken first, would Ernst still have insisted on going to retrieve Ivan's body? Dieter was always the hot-headed one in their trio; Ivan's moods were unpredictable; Ernst was known for keeping calm. But Ernst had known Ivan for longer – they were boyhood neighbours, always running in and out of each other's houses. Still, if Dieter hadn't complained about Commander Erwin's order to leave the bodies, would Ernst have let it go? Dieter desperately wants to believe that he wouldn't. He tells himself that Ernst was as determined to bring Ivan back as he was, if not more so. Ernst knew Ivan's parents; he was the one who wanted to return the body to them. But Ernst is dead too, now, and Dieter ought to be dead. If Mikasa hadn't saved him…
Later, lying on his bunk, unable to sleep, Dieter still holds Ivan's insignia. As the numbing shock begins to fade, giving way to sorrow and guilt that never will, it occurs to him for the first time that the Captain must have lied. At first he can't believe it – surely he's mistaken? Yes, lies are told in wartime. Informing the families of the slain that their loved ones are MIA rather than torn to pieces by titans might be kinder; no one has any illusions that a person lost beyond the walls will ever be recovered, and Dieter wouldn't wish the images he retains of Ernst's last moments on anyone. But a Captain lying to his own troops? Unthinkable.
Dieter tries to make Captain Levi's words possible a dozen different ways, but he can't do it. At last he gets out of bed and pulls on a clean uniform. The other is in the laundry, and the fact that he pissed himself when the titan's hand closed around him and lifted him towards its gaping mouth is the least of his shames. He stumbles through the dormitory in the semi-darkness, earning a few muttered curses and moans from fellow soldiers trying to sleep, prey to their own horrific memories of this latest disaster.
When he knocks on the door of the Captain's office, Dieter is surprised that it's Commander Smith who answers, still fully dressed, although minus his gear.
"Yes? Dieter, isn't it?"
"Yes, Sir. I – I wanted to see Captain Levi."
The Commander glances back into the room where Dieter can see a small form curled on a camp bed in a shadowy corner.
"He's asleep. Sedated. He was wounded this afternoon." The Commander looks exhausted himself, and Dieter's shame increases. Selfish, the sergeant had said. Squabbling kids, the Captain had called Ernst and Dieter. They'd both been right.
"I'm sorry, Sir. I shouldn't –"
"Wait there." The door closes and opens again a moment later. The Commander has put on his jacket and carries two uniform cloaks. He hands one to Dieter and closes the door softly behind him as he steps out into the corridor. "Follow me."
Commander Smith leads the way out of the barracks and across the courtyard to the base of the wall, where the counterweight elevator stands empty.
Atop the wall, the sentries salute smartly. The commander nods to them, and walks along the tracks a little way. When he stops, he turns to look out across the moonlit countryside beyond the wall, peaceful at night; a dream of a titan-free world.
"This is about the ones we left behind?" the Commander asks.
"No – not really. I – I mean, I understand, now. I was wrong. I should never -" Dieter can't think of the right words, so he holds out the insignia patch in mute appeal. Commander Smith takes it.
"Whose was this?" he asks.
"Captain Levi told me it was Ivan's."
The Commander gives Dieter a sharp look from under those heavy brows. "Ah."
"Only – I don't think… I mean, perhaps he made a mistake… because when we went back for Ivan – for his body - he was definitely wearing his jacket, and afterwards… I just can't see how… Unless Misaka – but she rode with me back to the wagon, so…" Dieter shrugs helplessly.
"I don't think it can have been Ivan's," the Commander says.
"But then, why would Captain Levi say it was?"
For the first time a shadow of something that could be anger crosses the Commander's face, but then it's gone, and it could just as easily have been a trick of the moonlight.
"It belonged to a brave soldier," the Commander replies, his voice quite calm. "Wasn't that your friend?"
Dieter considers the Commander's words. At last he nods. "Yes. He was brave. I was thinking of taking it to his parents, so they'd have something… Would that be wrong?"
The Commander looks down at the patch in his hands, and then passes it back to Dieter. "Do you think it would help them?"
Dieter feels tears threatening again, but he swallows them back. "Yes," he whispers. "Yes, I think it would."
"Do it, then." The Commander puts a firm hand on Dieter's shoulder. "You remember him, and your other friend who died. Ernst, wasn't it. That's all the proof you need that they lived. All we can do is to keep trying to make sure that their deaths have a purpose."
Dieter straightens, putting the insignia into his pocket. "Yes, Sir."
"Try to get some sleep. Oh – and I'd be grateful if you didn't let Captain Levi know that you saw through his subterfuge."
"Oh – no. No, I would never -. Of course. Thank you, Sir."
When Dieter has gone, Erwin Smith remains on top of the wall for a time, looking out into occupied territory. He thinks he knows whose insignia Levi must have given to the young soldier. There's only one he would have kept.
When he returns to Levi's office, the Captain is still sleeping. Normally he's a light sleeper, easily woken by any potential threat, but the sedative Erwin made him take is doing its job. Erwin hopes Levi's leg will heal well; without him the Survey Corps will be seriously diminished. He sighs, looking at Levi's still face in the low light of the gas lamp. Levi has learned a great deal over the years they've been working together, and he is without question the most skilled fighter the corps has ever known, but he's still no strategist. Even so, there's no one else Erwin would want as his second in command, and never has been. The people who call him cold - the ones who accuse him of having no humanity – those people know nothing at all.
There's still a lot of paperwork to do before the morning if they're going to be prepared for the damn tribunal that will probably be the outcome of this summons to the capital. Erwin seats himself behind the desk and turns the gas lamp up just enough to allow him to work. He picks up a pen, and starts to make notes, trying not to focus on the blue and silver wings at the top of the notepaper; the Survey Corps insignia, and everything it means.