Citrus Spark, in all his glory, has been invited to a big Enclave party in Canterlot. He's ready and raring to go.
Flick time forward a little, and a bright flash consumes the sky. Cloudsdale is hit.
Splendid Valley is next. Then Manehatten.
Then Hoofington.
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I am really crap at descriptions. Just read it and I'm sure you'll enjoy it.
I'm sorry but, you should probably Alternate universe this, since the Enclave did not even form until after the bombs fell.
Great start!
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That, and the very origin of the Enclave is that the pegasi stopped coming below the clouds by the end of the war, seeing the whole war as "the ground ponies' problems", so there being "a big Enclave party in Canterlot", as it said in the story description, is rather self-contradicting all on its own.