William Yeats' The Second Coming?

Question

Can you explain the meaning of the poem and also explain how it can be connected to 20th century events?

Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.

Surely some revelation is at hand;
Surely the Second Coming is at hand.
The Second Coming! Hardly are those words out
When a vast image out of Spiritus Mundi
Troubles my sight: somewhere in sands of the desert
A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds.
The darkness drops again; but now I know
That twenty centuries of stony sleep
Were vexed to nightmare by a rocking cradle,
And what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?

Answer 1

It is part of the power of this poem, that it has different meanings that overlap.
I can't help feeling that this poem represents, among other things, the historical events of the time (1920): The fall of the Ottoman Empire and rise of Arab nationalism ("things fall apart, the center cannot hold"); the rising of new power in Egypt (the Sphinx, the angry desert birds); WWI has just ended and new nations are being put together in the Middle East, one of them was Palestine, also called the Holy Land, which included Bethlehem and was administered by Britain in the hope of its being ready for independence some day; it was expected that a Jewish and an Arab section would be negotiated. Then as now there were passionate and (to the West) mysterious rivalries in the region. So the poem may express a wondering of what will "born" next at Bethlehem.
Of course this poem is powerful without any thought of its historical context. It can be interpreted in terms of the conflicts within the individual too; the disconnect between the mind and body symbolized by the falcon that doesn't respond to the falconer; the reconnection in the image of the sphinx.
He doesn't seem to be talking about the traditional idea of the Second Coming of Christ, but imagines that it will be quite different from what people think. This could well be true, of course, since humans cannot imagine what God imagines. The image of the "rough beast" that "slouches toward Bethlehem to be born" is disquieting. Does it represent a world-changing cataclysm coming to birth in the Middle East, rather than literally Christ? If so, it could be said to be prophetic! It also suggests that we don't always recognize Christ when we see Him, but may in fact see him as an enemy; that God doesn't see things as we do, or do what we expect.
He does comment on the people of the times, that "the best lack all conviction, while the worst are full of violent intensity." This also relates of the disconnect between the head and the body; those who use their brains are unfocused, like the falcon that can't hear the falconer, while there are violent and passionate forces which can lead to destruction.