These couplets from "Barbara Frietchie" by John Greenleaf Whittier move the action forward by describing the events that occur in the poem. The first couplet sets the scene by describing the soldiers halting, while the second couplet moves the action forward by describing the sound of the rifle blast and its effects on the surroundings, such as shivering the window and tearing the banner. Overall, the couplets create a sense of movement and action in the poem as the events unfold.