Hello...
Everybody worked together to move it to a remote mountain area, where they defended it for many days. For not a single day did they stop guarding it. Without their efforts, it might have been lost forever.
..........
In the above...
(A) Doesn't the underlined part have to be "Not for a single day ~"?
Or
(B) Are both possible?
Both are possible. I prefer Not for a single day. .
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