The poem is written in two different stanza forms, one form with shorter lines, the other with longer lines. The stanzas with shorter lines describe the making of the shield by Hephaestus, and report the scenes that Thetis expects to find on the shield and which Hephaestus, in Auden's version, does not make. Thetis expects to find scenes of happiness and peace like those described by Homer.
The stanzas with longer lines describe the scenes that Hephaestus creates in Auden's version, scenes of a barren and impersonal modern world. In the first, an anonymous, dispassionate army listens to a speech over a loudspeaker, a speech which uses impersonal statistics to argue that a cause is just; and the army marches off to be defeated. In the second scene, three anonymous prisoners are shamed and executed while a crowd of ordinary people watch passively. In the third scene, a "ragged urchin" throws a stone at a bird; he takes it for granted "that girls are raped, that two boys knife a third," and "has never heard of any world where promises are kept / Or one could weep because another wept."
In the closing stanza in short lines, Thetis cries out in dismay at what Hephaestus has made for her son, "who would not live long."
The poem is frequently cited as an antiwar poem, but it is also a study in language and responsibility: both Thetis and Hephaestus act on behalf of someone else, Achilles, and they take no personal responsibility for the results. And the results of their passive, impersonal stance is the passive, impersonal world portrayed on the shield.
An alternative reading: Auden reflects bitterly on the differences between the Achaean world as described by Homer—a world where, even amid warfare, imagination naturally ran to scenes of peace—and the world of totalitarian horror Auden himself imagine. At the same time, Auden criticizes Homer for attributing glory to warriors.
Auden's moral opprobrium is directed, not at Thetis or Hephaestus, but at "the strong iron-hearted man-slaying Achilles." The shield described by Auden is made by the god to please Achilles: the horrid world depicted there (and not the delightful world depicted in the shield described by Homer) is the natural result of the sort of iron-hearted manslaughter Achilles, and his comrades and rivals, practice.