Yeats wrote the poem in 1919 after the First Great War, but because of the Cristian imagery of the Apocalypse and the Second Coming, and its terrifying, ritualistic language, the poem is an obscure allegory open to several interpretations. May be that the poem looks simple in its structure, the first stanza describing the present conditions of the world-the state of disintegration and fragmentation as in things falling apart, anarchy being loosed, and the second stanza surmising that a monstrous Second Coming is about to take place, not of the Jesus as we knew, but of a new messiah, a “rough beast,” the slouching sphinx rousing itself in the desert and lumbering toward Bethlehem.
The opening lines describe a nightmarish scene: the falcon, turning in a widening “gyre” (spiral), cannot hear the falconer. Those who are the best lack all conviction, while the worst are "full of passionate intensity".
Then the poet/speaker asserts that the ''second coming'' is about to come. But he is troubled by “a vast image of the Spiritus Mundi, or the collective spirit of mankind: somewhere in the desert, a giant sphinx is moving, while the shadows of desert birds reel about it. What “rough beast,” he wonders "slouches towards Bethlehem to be born?”