I was going through some old books earlier this evening, and came across a poem called "Christmas: 1915," by a poet named Percy MacKaye, that concludes with the following lines:
Christ! What shall be delivered to the morn
Out of these pangs, if ever indeed another
Morn shall succeed this night, or this vast mother
Survive to know the blood-spent offspring, torn
From her racked flesh? -- What splendour from the smother?
What new-wing'd world, or mangled god stillborn?
Now, I'm not a Yeats scholar by any means, but this sounds very similar from a thematic standpoint to the famous final lines of Yeats' "Second Coming":
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?
The thematic similarities are unmistakable. Yeats' poem, as I understand it, was written in 1919. MacKaye's appeared in an anthology, A Treasury of War Poetry: British and American Poems of the World War, 1914 - 1917, that was published by the Houghton Mifflin Company in 1917. It seems plausible to me that Yeats might have encountered this poem two years before his own.
If the possible link between these poems is common knowledge, please forgive my bringing it up. But Mackaye's poem, though a very fine one, seems obscure enough to me that I believe it's possible no one has ever noticed this connection. I'd be interested in others' thoughts on this.