Albert Barnes Commentary 2 Kings 10:2

"And now as soon as this letter cometh to you, seeing your master`s sons are with you, and there are with you chariots and horses, a fortified city also, and armor;" — 2 Kings 10:2 (ASV)

A fenced city — Or, “fenced cities.” If Samaria had refused to acknowledge Jehu, many other Israelite towns would have been sure to follow the example.