Six short lines, and almost every word is doing double work. The title sets the tone: "Eaten by jingoes" suggests someone consumed by loud, flag-waving patriotism. The poem then pictures a road "of many lips," which reads like a path made of talk, slogans and cheering mouths. War isn't shown as battle here. It arrives as speech.
The final lines narrow things down to "a poor Jack," an ordinary man, perhaps a common soldier. War, the poem says, is "every raw expectation" placed on him. "Raw" carries a sting: untested, painful, exposed. The pressure of what others expect of him seems to be the real danger.
The speaker doesn't announce a feeling outright, but the mood is wry and uneasy. There's pity for Jack, and a quiet mockery of the crowd that sends him off. Judging by the imagery, the poem suggests that war feeds on talk and on the people who have to live up to it.