Just discovered moreutils after searching for "cat file sort and write to same file".

StackExchange told me that sort actually has an option to pseudo edit files "in-place" with the -o, --output options. But one of the more intersting (pun intended) google results described sponge found in moreutils.

Where you can do nifty things like:

$ sort conquest_eligible.txt | sponge conquest_eligible.txt