While Joshua was wondering how the Lord was directing him in to conquer Jericho, he suddenly encountered the Commander of the Lord's army. This being was the voice of YHWH. We refer to Him as a Christophany. That is to say Jesus before His incarnation. The battle plan was odd, to say the least, but Joshua did what we should do. He obeyed. The pattern is to get God's direction and do it regardless of how impracticable it seems.