Charles Ellicott Commentary Judges 20:35

"And Jehovah smote Benjamin before Israel; and the children of Israel destroyed of Benjamin that day twenty and five thousand and a hundred men: all these drew the sword." — Judges 20:35 (ASV)

Destroyed by the Benjamites ... — Here again we have a summary of the final result, followed by details, in a way that proves either that the narrative was compiled from various sources (one of which seems to have been a poem), or that it was written before the “periodic style” of history (lexis katestrammene) had been invented. If written consecutively, and not compiled, the writer must have been one whose method had the same resemblance to that of later writers as the style of Hellanicus did to that of Herodotus and Thucydides. It is the style to which Roman writers would have applied the epithet inconditus—the style of the oldest annals.

Judges 20:36–46 are not, as has been conjectured by some writers, necessarily a different account of the battle, but contain a loose assemblage of details, which has been added to explain the general result.