This verse must be read in connection with other Scripture passages. In the first place in concert with 2 Kings 8:20–22. There it says that Edom revolted from the rule of Judah. Now the opposite is happening, because Edom comes under the power of Judah again. Subsequently, when you place 2 Chronicles 25:5–16 next to it, you receive much more information as to how it all happened. And finally, 2 Kings 14:22 shows that father Amaziah started subjecting Edom and that his son Azariah finished it, for then Elath became (again) a city of Judah. That is important, for Elath was (and is) a harbour city and so Judah had a harbour at the sea again. It is fairly certain that the war with Edom was especially meant to secure the trade route and therefore the harbour of Elath was the final goal.
7 He struck down ten thousand Edomites in the Valley of Salt and took Sela by storm, and called it Joktheel, which is its name to this day.