Noble six hundred! (line 55)
Finally, even if the system might be lousy, even if the orders were wrong, Tennyson thinks these men are heroes. In this poem, doing your job is what counts. They did as they were told, without regard for their own safety, and that has made them worthy of our admiration. It's got to matter that this is the closing line. These ordinary men have become as noble as kings just by doing their jobs, and that's the last word on the subject.