The overriding tone of the poem is one of sustained anger, as the speaker sets out in unerring detail the horrors of the Spanish Civil War and the devastating impact it's had upon the town where he lives.

As the poem progresses, the mood becomes angrier still as the speaker describes an aerial assault by the Nationalist forces which has claimed the lives of many civilians, including children. In such an environment, it is impossible for the speaker to write poetry about dreams, leaves, and great volcanoes. The joys of nature have been eclipsed by all the blood-letting and the barbarism that has afflicted this beautiful land. All that's left for the speaker to write about is the blood in the streets.

After reading the poem, it's difficult not to feel a sense of futility at such an appalling waste of innocent life. There is very little hope in the poem, but that's entirely deliberate. For if there were any hope, it would doubtless detract from the message that Neruda wishes to convey. It would blunt the impact of the unrelenting misery that he depicts with such anger and conviction.