The poem opens with apostrophe, as the speaker directly addresses the instruments of a military band. The speaker enthusiastically tells drums and bugle horns to "beat" and "blow"—that is, to boldly announce their presence by making lots of noise. The poem was composed shortly after the Civil War's first battle, and Whitman supported the Union's cause. The opening line thus reads as a passionate rallying cry.
The poem's opening line is energetic and attention-grabbing, thanks to the alliteration of the /b/ sound, repetition (specifically epizeuxis and diacope), and caesuras. These devices add a strong rhythmic pulse to the poem's language that mimics the sound of forceful drumbeats:
Beat! beat! drums!—blow! bugles! blow!
These intense sounds convey the alarming disruption that comes along with war. For example, the speaker says that the noises of the military band "burst" through "windows" and "doors," as if nothing can keep the war at bay. The speaker uses a simile to build on this idea, comparing the war to a "ruthless force" that interrupts and overshadows everything in its path.
In keeping with this, the speaker describes the sounds of war tearing through "the solemn church," where it "scatter[s] the congregation." This is another example of how disruptive war can be, as it has the power to break into even the most sacred places (like church) and send the most calm, devoted people (a religious congregation) running in different directions. In other words, war turns peace and serenity into chaos.
Still, the speaker encourages the drums and bugles to interrupt everyday life. In this way, the poem implies that people shouldn't just go about their normal lives while war takes shape. The poem at once urges people to pay attention to the Civil War while acknowledging its horror and ability to grind society to a halt.