News of a war arrives, and the speaker reacts at once, almost without thinking. He cuts off his beard and washes his feet in the sea. Both actions feel like a kind of private ritual, a stripping away of his everyday self, as if he were making himself ready for something he doesn't quite understand. The phrase "sudden fit" tells us this isn't a calm decision.
The last three lines widen the view. A uniform, the speaker suggests, will turn people "of all sides" mad, each one convinced the king expects them. There's dry, bitter irony here: the same belief in being personally summoned drives soldiers on every side, so no one's sense of purpose is special. The mood is quiet and uneasy. The images are small and physical, but they sit beside a sharp observation about how easily people give up their individuality and let a uniform and a sense of duty speak for them. The speaker seems to be both caught up in this and watching it from a distance.