Though they were assured of the success by a particular and absolute promise, yet they do not neglect the use of means; as well knowing that the certainty of God's purposes or promises doth not excuse, but rather require man's diligent use of all fit means for the accomplishment of them. Round about Gibeah, i.e. on several sides of it, as may be gathered from the following verses.
Related Commentaries of Judges 20:29
Judges 20:29
29 And Israel set liers in wait round about Gibeah.