**The Exile** of the tribes of Gad, Reuven, and half the tribe of Menasheh appears to have been at the end of the days of Pekach, as it says [(Melachim II 15)] "In the days of Pekach king of Yisrael, Tiglath-Pileser king of Ashur came and took Iyon and Avel Beit-Ma'achah, etc." This was in year 3187, the end of Pekach's days, according to the Rashban in the introduction to Eichah Rabbati [(Tzeda) (but I have seen that this is not the Rashban's view, and these are his words: Rabbi Elazar says the tribe of Reuven and Gad were exiled first. And Yefeh Anaf writes: Rashi in Yeshayahu (chapter 8) brings Seder Olam that the exile of Zevulun and Naftali was in the days of Pekach, the 5th year of Achaz, and the exile of Reuven and Gad was in the 12th year of Achaz at the beginning of Hoshea's rebellion, and this is according to the view of the Rashban who says that Zevulun and Gad were exiled first, thus far, but this is a typographical error, for what it says is the view of the Rashban is actually the view of Rabbi N, and so forth)].
The Ralbag wrote that this was the exile of Gad, Reuven, and half the tribe of Menasheh. Rashi explains that the exile of the two and a half tribes was in the 12th year of Achaz [(and so in Seder Olam, proven in Yalkut Melachim II 18, but there's a typographical error there that writes 12th of Pekach, and it should be Achaz)], in the days of Hoshea son of Elah in the year of his rebellion against the king of Ashur, which was year 3195.
But the words of the Ralbag are not apparent, because Scripture says in Divrei HaYamim 5 "And the God of Yisrael stirred up the spirit of Pul king of Ashur and the spirit of Tiglath-Pileser king of Ashur, etc.," but Scripture does not explain at what time this was. It only revealed to us that the exilers were Pul and Tiglat, kings of Ashur, and when it says "Tiglath-Pileser came," apparently it is the same matter as the second.
Also, Scripture says that Hoshea rebelled against Shalmaneser king of Ashur, not Tiglath-Pileser, and according to this, this exile was 18 years before the exile of the rest of the tribes [thus far Tzeda. In Sha'ar HaDorot 18 section 2 it says that at the end of Pekach's days the two and a half tribes mentioned above and the golden calf of Yarov'am were exiled and taken to Chalach and Chavor and the river Gozan, and this was the first exile (which is the view of the Ralbag).
And it further writes that Hoshea son of Elah became king over Yisrael for 9 years (meaning from the day of his rebellion, which is year 3195), then Sancherev returned with a sword and exiled all the remaining Yisrael and the entire kingdom of Shomron and the second calf that was in Beit El with them, and sent them both to Chalach and Chavor and the river Gozan, and this was in the 12th year of Achaz (a typographical error, for in Melachim II 7 it says "in the twelfth year of Achaz king of Yehudah"), Hoshea became king in Shomron for 9 years, which is year 3195, and this is the second exile of Yisrael. And it writes that in the 5th year of Chizkiyahu (which is year 202 or 203) Sancherev came a third time to Shomron when there was no king in Yisrael and conquered it in six years (it should say eight years, for the second exile was in year 3195 and this was in year 203), after the second exile, and he exiled the tribe of Efrayim and Menasheh who remained there, and this was the third exile in year 3206, thus far.
According to my understanding, as appears in Tzeda, the exile of the 12 tribes was in year 205, so 3195 was the exile of some tribes, as appears from Rashi's language (Melachim II beginning of chapter 17): "In two exiles the 12 tribes were exiled: in the 20th year of Pekach, the 5th of Achaz (which is 3187) and the 12th of Achaz (which is 3195), and the 9th of Hoshea's rebellion (which is 205) they were all exiled." And this is what it says (Yeshayahu 9:2): "At first He made light the land of Zevulun and the land of Naftali, He made light" — even though it only exiled 2 tribes, but the latter made heavy like one who extinguishes the house, see there. So it appears that the exile of the 12 tribes was in year 205, not according to the view of Sha'ar HaDorot mentioned above that it was in year 3195, and this needs clarification.
And as appears in Seder Olam proven in Yalkut mentioned above: "As the shepherd rescues from the lion's mouth two legs" — these are the 12 tribes who relied on Chizkiyahu and escaped with them, thus far. And if it were according to the words of the Sha'ar HaDorot that in year 3195, the first year of Hoshea's rebellion, all Yisrael was exiled when Chizkiyahu was not yet king until year 3198, how can it be said that the 12 tribes relied on him?
Also, Sha'ar HaDorot writes that in the 5th year of Chizkiyahu's reign Sancherev came a third time to Shomron when there was no king in Yisrael — this needs clarification, for the 5th year of Chizkiyahu was the 6th of Hoshea, as explained in the chapter, and then Hoshea was king. And it seems plausible at first that the 14th year of Chizkiyahu, which was year 212, was 8 years after the exile of the 12 tribes.
But it is explicitly stated in the chapter that in the 14th year of Chizkiyahu Sancherev came against the cities of Yehudah, but in the 5th year of Chizkiyahu he came against Shomron.
Furthermore, the 11th year of Chizkiyahu was the fourth exile, yet he writes the third exile, and this needs clarification].