The head here is a reference to the human heads, both Rezin and Pekah, who are the heads of state of both Syria and the northern kingdom of Israel.
By implication, Judah has no human head, but a divine head, namely God.
Thus the controversy here is between the will of man, versus the will of God.
Isaiah has already stated that these two countries are at the tail end of their existence. And now, there is a specific date given as to how long Syria and the northern nation of Israel will last, and then be no more.
This is to provide Ahaz with some comfort, knowing that Judah will be safe and in tact, at least for the time being.
Ephraim is often times used synonymously as a reference to the northern nation of Israel, which was made up of the ten tribes that split away from Judah and Benjamin, after the death of Solomon.
That split occurred around 980 B.C. So now we are some two centuries later and Israel has now been given only 65 years more, and then will be no more.
The point of all of this is to give assurance to Ahaz, the king of Judah, that the impending invasion of Syria and Israel, into Judah, will not accomplish anything, and Judah will remain in tact.
The date of this prophecy is dated in the second year of the reign of Ahaz, and sixty five years later during the twenty-second year of the reign of Manasseh, then the northern nation of Israel, the ten tribes that made up that country, was finally destroyed.
Only a couple of years after this prophecy, the Assyrian king Tiglath-pileser invaded Israel and carried away many captives, 2 Kg 15:29. In the next reign of Hoshea the king of Israel, there was yet another invasion by Shalmaneser and many captives were taken away, 2 Kg 17:1-6. This was in the twelfth year of the reign of Ahaz.
But it was not until the time of Esarhaddon of Assyria, sixty-five years after this prophecy, when the remaining residents of Israel were removed and thus the end and vanishing of the northern nation of Israel.
Thus Isaiah’s prophecy, that they be not a people, was fulfilled.
After Solomon’s death, the ten tribes rebelled and rejected the line of David. That is the same as rejecting Gods will and promise that the Messiah would descend from David and thereby establish that dynasty forever. Rejecting the Davidic line is equal with rejecting the Messiah.
For those who reject the Messiah, their destiny is to vanish from history and to be no more. And therefore, symbolically, the northern nation rejected God and the Savior and as a result of their choice, they vanished from history.
When we all get into the next life and into eternity, then all unbelievers will have vanished from our sight, and from our memories, and will be forever forgotten. For us, there will be no thought of them, no memory of them, no recollection of them, nothing.
It will be as though they never existed and therefore there will be nothing to remember. And for us as believers, that removal of remembrance will be a good thing, lest we might be sorrowful for someone that we once knew, but they did not believe and did not make it into heaven.
The blessing of forgetting will prevent any form of sadness for someone else that is not there. And that is a good thing.
End of study