The settlement of the Israelite tribes on the eastern side of the Jordan River concludes with the tragedy of their exile. This historical shift was orchestrated by God, who awakened the desire of the Assyrian king to carry out this decree [מצודת ציון, ביאור שטיינזלץ].
The historical record names Pul and Tiglath-pileser as the Assyrian forces involved, though their exact identities present an interesting discussion. One perspective suggests that these names refer to a single monarch, also known as Sennacherib, who operated under multiple titles [רלב״ג]. However, another approach views them as two distinct kings who ruled at different times, indicating that the exile occurred in devastating stages rather than a single event. According to this understanding, Pul first arrived during the era of Menahem son of Gadi, taking the tribe of Reuben and a portion of Gad into captivity. The remaining members of Gad and the half-tribe of Manasseh stayed in the region of Gilead and continued to grow. Eventually, Tiglath-pileser arrived during the time of Pekah and exiled the rest of the population.
This initial removal of Reuben and Gad had a profound spiritual impact on the entire nation. Because the Land of Israel was no longer fully populated by all of its inhabitants, the observance of the Jubilee year was officially canceled [מלבי״ם].
The captives were taken to the northwestern regions of the Assyrian empire, encompassing areas known today as northern Media, northern Syria, and Iraq [ביאור שטיינזלץ]. They were settled along the banks of the Gozan river [מצודת דוד]. Eventually, the rest of the ten northern tribes would be exiled to these exact same locations, though other historical records refer to these areas as the cities of Media [רלב״ג].
The tragedy of this event is cemented by the fact that these tribes never returned to their homeland. Years later, when the exiles of Judah departed from Babylon and returned to the Land of Israel with Ezra to rebuild the Second Temple, the eastern tribes did not join them. They remained scattered in their places of exile, permanently separated from their land.