Yeats expresses mixed feeling about the Easter Rising of 1916. In it, rebels rose up to fight against British rule in Ireland. Yeats supports their nationalism: he wants Ireland to be freed of the oppressive British government that has for so long held the country down. He also fears that the rebels, the leaders of whom were executed, perhaps behaved too rashly and violently.
Yet the main point is that the poem supports and applauds the cause of Irish nationalism and mourns the execution of the rebels. His speaker, for example, states: "We know their dream."
He speculates that perhaps they acted out of an "excess of love" for their country. This may have "bewildered" (confused) them so that they acted too rashly—but the love itself was a good and pure impulse.
He also uses positive imagery to describe the rebels: their hearts have "one purpose" and they are agents of change, aligned to the forces of nature, suggesting that what they want is a natural thing:
From cloud to tumbling cloud,
Minute by minute they change ...
Rather than condemn the uprising as an ugly blot, the speaker frames it as a creative act from which beauty has been born, stating repeatedly throughout the poem:
A terrible beauty is born.
He states too that the cause of Irish nationalism will not be the same after this uprising, saying that anyone who wears "green"—supports the cause of Irish independence—has been changed by this action: "changed, changed utterly."
Yeats's poem is often seen as prophetic, as the Irish did achieve their nationalist goal of independence not long after this. The tone of the poem paints their nationalism as a desirable aim.