“he will root up Israel out of this good land that he gave to their fathers and will scatter them beyond the Euphrates River.” This amazing prophecy by Ahijah the prophet was spoken during the reign of Jeroboam I of Israel, and far enough into his reign that the evil set in motion by Jeroboam would have had some time to be ritualized and set in the culture. So this prophecy would likely have occurred somewhere around 930 BC, a full 200 years before Israel was finally destroyed by the Assyrians and carried away captive to parts of Assyria in 722 BC (2 Kings 17:6-23).
The Hebrew text just reads, “the river,” not the Euphrates River. In biblical times, the Euphrates was often just referred to as “the River,” and that is the case here. This prophecy of Ahijah was fulfilled when the Assyrians conquered the country of Israel and carried them beyond the Euphrates (2 Kings 17:1-23).