Richest countries unprepared in retrospect for conflict (5,5,3)

I believe the answer is:

first world war

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'richest countries unprepared' is the definition.
I can't judge whether this defines the answer.

'retrospect for conflict' is the wordplay.
'retrospect for' becomes 'first' (I can't justify this - if you can you should give a lot more credence to this answer).
'conflict' becomes 'world war' (I have seen 'Global conflict' mean 'world war' so perhaps 'conflict' could also mean 'world war').
'first'+'worldwar'='FIRST WORLD WAR'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for first world war that I've seen before include "hostilities" , "20th-century conflict" .)

I've seen this clue in The Times.

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