In what way, according to Thoreau, are soldiers "men of straw," or "lump[s] of earth"?

According to Thoreau, men of "the standing army, and the militia, jailers, constables, posse comitatus, etc." perform their duties like machines, doing what their told without thought.

The mass of men serve the state thus, not as men mainly, but as machines, with their bodies. They are the standing army, and the militia, jailers, constables, posse comitatus, etc. In most cases there is no free exercise whatever of the judgment or of the moral sense; but they put themselves on a level with wood and earth and stones; and wooden men can perhaps be manufactured that will serve the purpose as well. Such command no more respect than men of straw or a lump of dirt. They have the same sort of worth only as horses and dogs.