Moore's "War Song" opens with an order: "Remember." The poem is a call to arms, but it begins by looking backward. The speaker is a soldier addressing fellow soldiers. He summons the dead king Brien (Brian Boru, the medieval Irish ruler remembered for his fight against the Danes) and the comrades who fell on "Ossory's plain," and he asks the living to be worthy of both. Its central idea is that the dead are not simply lost. Their glory is a kind of energy that the living can use, and they also leave a debt that has to be repaid.
The imagery of light carries this idea. Brien is "that star of the field," whose beam has often fallen "on the battle." Stars set, and the poem admits it: "is set." Then comes the turn in the final lines of the first stanza: "enough of its glory remains on each sword, / To light us to victory yet." The hero's light is now borrowed, shining from the blades of ordinary men. The same image returns in the last stanza, where the sun "blesses our arms with his light." Here the sun becomes a witness, and the speaker fears it might "blush" at the end of the day. A line that sounds like a prayer is really a threat held over the soldiers' own heads. If they fail, the sun will have watched the dead die "in vain."
The second stanza moves from memory to defiance. It begins as a landscape painting: Nature "embellish'd the tint" of Mononia's fields and mountains. Then comes a rhetorical question about whether she ever meant "a tyrant should print / The footstep of slavery there." The verb "print" makes the invader's boot a stain on a finished picture, so conquest becomes both a moral and an aesthetic wrong. The shout of "No!" answers the question, and Freedom is addressed directly and asked to tell "our invaders, the Danes" what the Irish choose. Their choice is built into one balanced line: it is "sweeter to bleed for an age at thy shrine, / Than to sleep but a moment in chains." The comparison is neat, though "sweeter" is a startling word to use about bleeding. It presents sacrifice as something almost to be savoured, which is the sort of claim a war song needs to make.
The form suits the purpose. Each stanza is eight lines rhymed ABABCDCD, and the rhymes are mostly simple and full: "brave" with "grave," "light" with "to-night," "plain" with "vain." In the third stanza "stood" and "blood" are only an imperfect match, and the slight roughness lands on the most violent image in the poem, the "moss of the valley" growing "red." The metre is lilting and anapaestic, with four beats in the long lines and three in the short ones. The first line gallops: "Re-MEM-ber the GLO-ries of BRI-en the BRAVE." The shorter lines that follow, such as "He returns to Kinkora no more," drop a beat, so each couplet of lines rises and then falls. The effect is like a march that stumbles on the memory of loss and then picks up again. It is easy to imagine the words being sung, and the title "War Song" invites that.
Moore also shapes the poem through verbs. "Remember," "Forget not," "Go, tell" and "let him not blush" are all imperatives or negative commands, so the whole poem is pitched as persuasion. The wounded comrades are given the plainest and most moving line: "They stirr'd not, but conquer'd and died." The pairing of "conquer'd" and "died" shows how the poem measures heroism, since death is part of the victory and does not cancel it.
The Danes are the named enemy, but the poem's argument is general enough to be applied to any occupier. Judging by the way it speaks of "tyrant," "slavery" and "chains," a reader could easily hear a more recent political echo, though the poem itself never says so. That openness is part of its significance. It turns a distant battle into a model for how a community can use its dead, with grief becoming resolve and the past becoming a standard. The poem also leaves a question hanging over its final image, because the sun is still setting and the dead are still waiting to find out whether they died "in vain."