After the war, Billy will cry suddenly, out of the blue. But he never makes loud sobbing noises.
This is why the narrator has chosen "Away in a Manger" as the epigraph for the novel: like the little Jesus in the Christmas carol, "No crying [Billy] makes" (9.21.2).
Billy travels in time to his hospital bed in Vermont, where Rumfoord has finally decided that, yes, Billy was at Dresden.
He asks Billy what it was like, and Billy tells Rumfoord about the horses and the moonscape of the ruined city.
The story ends like this: Billy and the doctors unharness the horses, but they don't go anywhere because their feet hurt too much.
Just then, the Russians come in and arrest everyone.
Two days after that, Billy gets turned over to the American authorities, who send him home.
A minor observation: the narrator specifies that Billy gets sent home on a ship named after American women's rights activist Lucretia A. Mott. But Lucretia Mott's middle name was Coffin, so it would be Lucretia C. Mott. Accident? Or deliberate substitution because Vonnegut didn't want to talk about Coffins in this scene. Who can say?