War and the army. That's all we hear when we listen to this poem.
The speaker is clearly some kind of military man, and he certainly talks like one, especially in that annoying refrain "Do not weep. War is kind" (4-5, 15-16, 25-26). Those short, gruff, cold, icy, freezing sentences sure sound like they are spoken by some sort of military commander, doing his best to sound less like a cruel robot.
And they're not the only ones, either. In fact, the speaker often favors short, staccato-like clauses. Military men are all about business, and they're not in the habit of using long, complicated sentences. Take lines 6-8 as an example: "Hoarse, booming drums of the regiment, / Little souls who thirst for fight, / These men were born to drill and die." Tell it like it is, why don't you. These lines are no nonsense, no frills.
Since this is a poem about war, we can't help thinking that these short clauses sound like bullets firing in succession—tat tat tat tat tat tat tat—which makes a lot of sense when you consider that we really do hear the battlefield in this poem, and we hear it all the time. Words like "booming" (6) and "blazing" (17) make us think of bombs, guns, fires, and all that, but they also sound like those things. They're onomatopoetic, if you want the fancy shmancy term for it.
Alongside the sounds of the battle, we can also hear that military guy barking orders. Case in point: "Point for them the virtue of slaughter, / Make plain to them the excellence of killing" (20-21). Granted, the speaker is in kind of a little reverie here, but the sentences sure have the ring of an order. Can you hear it? A line of soldiers, a guy giving commands: "POINT! MAKE PLAIN!" Yes sir.