Because Jehu was unfaithful, the Lord started reducing Israel's territory. This was one of the curses for breaking the covenant (Deuteronomy 28:25).
The Aramean king Hazael moved south, taking over areas east of the Jordan River, north of Moab's border. The Arameans kept pressuring Israel during Jehu's rule and into his son Jehoahaz's reign (2 Kings 12:17–18; 13:3).