‘ And the liers in wait acted speedily, and rushed on Gibeah, and the liers in wait drew (or ‘extended') themselves along and smote all the city with the edge of the sword.'
“Drew themselves along” may describe some tactic used. It may mean extended themselves along so as to attack over a wide range. This would make it more difficult for slingers. Or it may refer to what they did on entering the city, spreading out to slay all the inhabitants they could find. Whatever it was their tactics were successful.
The weakly defended city, with only one fighting unit available, was unable to stem the onset and succumbed, and all were put to the sword for they were seen as sharing the guilt of Gibeah. They were subject to The Ban, total extermination, for working folly in Israel, as with Achan and his family (Joshua 7:15).