en_tn/2ch/15/06.md

They were broken in pieces, nation against nation, and city against city

The word "they" refers to the words "nation" and "city." Conquering one another is spoken of as if they were breaking each other into pieces. AT: "Nations and cities destroyed each other, nations fighting nations, cities fighting cities" (See: rc://en/ta/man/translate/figs-metaphor)

They were broken in pieces, nation against nation, and city against city

Here "nation" and "city" are metonyms for the people who live there. You may also supply a connecting word to clarify the relationship between these two phrases. AT: "Nations and cities destroyed each other, as the people of one nation fought against the people of another nation, and the people of one city fought against the people of another city" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/writing-connectingwords)